RiverRiver RestorationRestoration – Danish experience and examples

National Environmental Research Institute River Restoration – Danish experience and examples Editor: Hans Ole Hansen

Editor: Hans Ole Hansen RiverDepartment Restoration of Streams and Riparian Areas – Danish experience and examples

Ministry of Environment and Energy National Environmental Research Institute 1996 Ministry of Environment and Energy National Environmental Research Institute 1996 River Restoration – Danish experience and examples

Editor: Hans Ole Hansen, Department of Streams and Riparian Areas

Published by: National Environmental Research Institute©, Denmark

Publication year: September 1996

Translation: David I. Barry, On Line Activities

Layout: Kathe Møgelvang and Juana Jacobsen

Cover picture: J.W. Luftfoto and Sønderjylland County

Printed by: Silkeborg Bogtryk

ISBN: 87–7772–279–5

Impression: 600

Price: DKK 150 (incl. 25% VAT, excl. postage)

For sale at: National Environmental Research Institute Vejlsøvej 25, P.O. Box 314 DK–8600 Silkeborg, Denmark Tlf. +45 89 201 400 – Fax +45 89 201 414

Miljøbutikken Information and Books Læderstræde 1 DK–1201 Copenhagen K, Denmark Tel.: +45 33 379 292 (Books) Tel.: +45 33 927 692 (Information) Contents

1 Introduction 5

2 From idea to reality 13

3 Completed watercourse rehabilitation projects 21 3.1 Tøsbæk/Spånbæk brook at Dybvad 22 3.2 Pump station at Gjøl 24 3.3 Lerkenfeld stream at Østrup 26 3.4 River Storå at Holstebro 28 3.5 Idom stream at Idum 30 3.6 Rind stream at Herning 32 3.7 River Gudenå at Langå 35 3.8 Lilleå stream at Hadsten 37 3.9 Lammebæk brook at Daugård 39 3.10 Kvak Møllebæk brook at Skibet 41 3.11 River Brede at Løgumkloster 43 3.12 River Brede at Bredebro 46 3.13 River Odense at Ejby Mølle, Odense 48 3.14 River Odense at The Seahorse, Odense 50 3.15 Lindved stream at Hollufgård, Odense 52 3.16 Holmehave brook at Borreby Mill, Odense 55 3.17 Esrum stream at lake Esrum 58 3.18 Græse stream at Frederikssund 60 3.19 Store Vejleå stream near Glostrup 62 3.20 Køge stream at Lellinge 64 3.21 Køge stream at Bjæverskov 66 3.22 River Suså at Holløse Mill, Skelby 68 3.23 Lilleå stream at Kongsted 70 3.24 Søbæk brook at Neksø 72

4 Classification system for watercourse rehabilitation 73

5 Environmental impact of watercourse rehabilitation 80

Appendix A 91

References 98 3 1 Hans Ole Hansen Bent Lauge Madsen Introduction

There are approximately 30,000 km of Watercourse Act, for example with watercourse of natural origin in Denmark, respect to watercourse maintenance. and an equivalent length of man-made watercourses. This should provide good Watercourse environmental quality opportunities to enjoy nature, as well as a objectives multitude of habitats for a diverse flora The original Danish Environmental and fauna. Protection Act from 1974 encompassed a However, during the course of this planning system that in the case of century the majority of our watercourses watercourses, was implemented in the have been channelized to drain agricultural form of a system of specific quality land, freshwater fish farms, industry and objectives, a system that has played, and urban areas. Channelization was often still plays, a crucial role in endeavours to accompanied by the construction of weirs safeguard watercourse environmental and other obstructions, and in many quality (Box 1.1). The environmental cases these effectively hindered the free quality objective for each watercourse is passage of fish and stream macroinverte- set forth in the County Plan. In setting brates. As a result, there are now only the objectives, the County takes into few watercourses that live up to our ideas account the natural state of the water- of a natural watercourse. The situation is course, what impact man has had, the starting to improve, though, partly as a intended use of the watercourse, and result of changes and improvements in what can realistically be achieved. the administration of our watercourses. Through this system of quality objectives it has been possible to differentiate between different watercourses and Danish watercourse concentrate efforts where they are of administration greatest benefit. The two main laws governing Danish watercourses are the Watercourse Act Pollutional state of Danish and the Environmental Protection Act. watercourses From the administrative point of view, The County has supervisory responsibility Danish watercourses are divided into for the pollutional state of all water- three groups: County watercourses, courses. Pollutional state is evaluated by municipal watercourses and private investigating the macroinvertebrate fauna watercourses. The County is the water- inhabiting the watercourse, and is rated course authority in the case of county on a scale from I to IV. I corresponds to a watercourses, while the Municipality is watercourse with a very varied macro- the watercourse authority for both invertebrate fauna while IV corresponds municipal and private watercourses. The to one with a very uniform or absent watercourse authority’s task is to ensure fauna. The national streampollution compliance with the provisions of the monitoring network comprises 220 5 Introduction

effect on water quality due to increased various types of rehabilitation project and The environmental quality objective for each Danish loading with ochre, etc. methods, and to evaluate their impact. watercourse is set forth in the County Plan. The In 1994, the Danish Environmental County Council can choose between a variety of Restoration or rehabilitation Protection Agency, the National environmental quality objectives, or they can formu- Considerable work still needs to be done Environmental Research Institute and the late their own objectives. In principle, there are three to improve the physical condition of our 14 Danish Counties therefore initiated groups of watercourse quality objectives: Stringent watercourses if watercourse quality is to the project “Watercourse restoration – (A), basic (B) and eased (C, D, E, F). The objectives are match up to the increasingly good quality Methods and effects”. The main aim of as follows: requirements stipulated for stream water. the project was to collect and collate This can be achieved through environ- existing knowledge on restoration A: Areas of special scientific interest mentally sound watercourse maintenance methods and their effects. The present B1: Salmonid spawning and nursery waters as well as through various types of book, which is partly built up around B2: Salmonid waters restoration measure. Since these two examples from the counties, is the first B3: Cyprinid waters approaches are usually combined with result of this project. B4: Watercourses with a varied flora and fauna but the general objective of improving the A further aim of the project was to of little value to fish physical condition of our watercourses, it describe the physical conditions required C: Watercourses to be used for drainage purposes is useful to use a term that encompasses by the fish inhabiting our watercourses. D: Watercourses affected by waste water both environmentally sound maintenance Fish are a good indicator of watercourse E: Watercourses affected by water abstraction and restoration measures. quality, and an understanding of their F: Watercourses affected by ochre In this book, we have chosen to use requirements is an important tool when the term watercourse rehabilitation, a planning restoration or changing main- term gaining increasing acceptance in the tenance practice. If conditions are good stations where pollutional state is Box 1.1. scientific community. When the measure for fish, they are usually also good for monitored annually. In addition, though, Watercourse used only involves a change in the stream macroinvertebrates and plants. the individual county authorities monitor environmental physical condition of the watercourse The results of this part of the project have pollutional state less frequently at many quality objectives. (excavation, etc.), we use the term been published as a report describing the hundreds of additional stations. watercourse restoration. conditions required by all Danish freshwater fish (1). Action Plan on the Aquatic 15 years’ experience Environment With the advent of the new Watercourse In 1987, the Danish government passed a Act some 15 years ago, it became legally The European Centre for new Action Plan on the Aquatic Environ- permissible to rehabilitate Danish water- River Restoration (ECRR) ment aimed at considerably reducing courses. This possibility has been ex- Since the first international conference in nutrient and organic matter loading of ploited, and over the years, numerous 1991 in Lund, Sweden (2), on river the aquatic environment. Since adoption rehabilitation projects have been carried restoration there has been an increasing of the Action Plan, the quality of the out – ranging from the laying out of European interest in restoring water- water in our watercourses has improved spawning gravel to major projects aimed courses and river valley ecosystems for year by year, largely due to the upgrading at remeandering watercourses and the benefit of wildlife. At the same time, of sewage works. However, clean water improving the interplay between water- there is increasing awareness that alone is not sufficient to ensure satisfac- courses and their river valley. reinstating naturally functioning water- tory watercourse quality. If the water- However, rehabilitation projects are course-river valley systems also yields course lacks physical variation, habitats seldom followed up by studies of the catchment management benefits, for the flora and fauna will be limited in impact of restoration on biological, particularly by increasing flood water number and quality. At the same time, chemical and physical conditions in the storage capacity, enhancing nutrient poor physical conditions often have a watercourses and their riparian areas. retention and ameliorating low discharge. negative impact on water quality because Similarly, the experience gained from the Sustainable management and restoration oxygenation and self-purification will be individual projects is seldom published, of watercourses and river valley ecosys- less effective. Similarly, drainage of and hence is seldom of benefit to others tems may also reduce river maintenance riparian areas can also have a negative working with watercourse rehabilitation. costs and provide better amenity and There is therefore a need to describe the recreational facilities. 6 Introduction

Danish regional and national European Centre for River Restoration river valley management and restoration, authorities have accumulated considerable as well as the dissemination of the ECRR experience and know-how regarding information to the European audience watercourse and river valley management through newsletters, conferences, and restoration during the last decade, workshops, technical handbooks, videos, both with respect to legislation, conser- European Network etc. In addition, the ECRR and the vation and administration, as well as to NERI Network will promote watercourse and practical experience in carrying out Denmark river valley management and restoration different management and restoration through the initiation of Demonstration measures in river systems and monitoring Projects in each European country. These of their ecological effects. activities will ensure that knowledge on Environmentally sustainable manage- National Network river and river valley management and ment and restoration of watercourses was restoration will be communicated to the included in the Danish Watercourse Act Figure 1.1. NERI is a sectorial research institute widest possible European audience for as early as 1982, and in 1987 nature The European under the Danish Ministry of Environment the benefits of Nature and Society. restoration was introduced as an element Centre for River and Energy and is the Danish National The present volume is the ECRR’s first of the 1987 “Strategy on Marginal Restoration and the Focal Point for the European Environment handbook and is intended to demonstrate Lands”, the aim of which was to restore European River Agency (EEA). In addition, NERI to the European audience the experience 20,000 ha of former wetlands. More than Restoration departments currently participate in three accumulated in Denmark on watercourse 1,000 small and larger-scale river Network. European Topic Centres, undertaking and river valley management and restoration projects have so far been projects for the EEA in international fora restoration. For further information you undertaken, primarily by the Danish concerning monitoring, establishment of are welcome to contact the ECRR in Counties and Municipalities. databases, etc. NERI currently has around Silkeborg. The Centre can demonstrate The National Environmental Research 450 members of staff, as well as 30 PhD Danish experience via posters and videos Institute (NERI) is the national platform in students and 56 MSc students. and can arrange for tours to Demonstra- Denmark for monitoring and scientific The main aims of the ECRR are to tion Project sites in various parts of research on watercourse and river valley promote sustainable watercourse and Denmark. management and restoration. In Denmark river valley management and restoration watercourse and river valley management measures and ensure widespread take-up The ECRR’s address and telephone and restoration projects are mainly and dissemination of related manage- number is as follows: undertaken by the Counties and ment and restoration activities. The municipalities with the support of the Centre focuses on establishing a state-of- Danish Environmental Protection Agency the-art information base on watercourse European Centre for River Restoration and the Danish Forestry and Nature management and restoration of natural National Environmental Research Institute Agency. NERI collaborates with the local habitats in damaged watercourses and Vejlsøvej 25, P.O.Box 314 and central authorities on the collection their river valleys. This will be achieved DK-8600 Silkeborg, Denmark of information on watercourse and river using experience gathered in the Euro- Tel. +45 89 201 400 valley management and restoration and pean Countries concerning watercourse Fax. +45 89 201 414 the dissemination of the experience management and restoration concepts e-mail [email protected] gained through newsletters, workshops, and methodology, as well as on the training courses, technical handbooks, planning, execution and impact videos, etc. monitoring of restoration projects. In 1993, the EU Life Programme The aims of the ECRR will be achieved Basis for watercourse granted funds to establish a major through developing a European Network rehabilitation European Demonstration Project in of relevant national institutions (Figure 1.1). Watercourse rehabilitation is purposeful Denmark and the United Kingdom led by The Centre and the European River improvement of the physical and ecologi- the Sønderjylland County. As part of this Restoration Network will collaborate on cal condition of watercourses. It is a rapid project the European Centre for River ensuring the collection and assessment of and direct means of achieving the Restoration (ECRR) was established at experience and knowledge obtained improvements one would like to see take NERI in Silkeborg in 1995. throughout Europe on watercourse and place in watercourses, and in some cases 7 Introduction is the only means. In the present spirit of things in Denmark, rehabilitation only Watercourse Act of June 9, 1982 Act of June 14, 1995 amending encompasses measures that improve the the Watercourse Act quality of watercourses as natural PART 8 ecosystems or as angling waters. The Restoration of watercourses specific aim of rehabilitation can be to change the watercourse’s appearance, to 37.— (1) In the case of public watercourses whose condi- 37 a.—(1) In watercourses where create habitats for the fauna and flora, to tion does not fulfil the regional water quality objectives, sluices are highly detrimental to restore free passage or to improve the the watercourse authorities are empowered to improve watercourse quality, the County watercourse’s self-purification properties. conditions by means of the following measures: Council can decide pursuant to the Rehabilitation (restoration) was (a) the establishment of artificial overhanging banks, provisions of this Act to implement incorporated in the new Danish (b) the laying out of large rocks, whatever measures are necessary to Watercourse Act in 1982. The individual (c) the laying out of logs and the like on the restore satisfactory environmental measures are described as five simple watercourse bed, quality, including regulating the methods (Box 1.2) – methods that to (d) the establishment of current concentrators and watercourse. present Danish eyes provide extremely (e) the establishment of spawning grounds. (2) Measures pursuant to subsection (1) limited possibilities to rehabilitate may not be implemented if to do watercourses. That they are so limited is (2) The watercourse authorities defray the expenses of so disregards significant historical partly due to the misgivings with which restoration. interests. the restoration concept was received by (3) The Environmental Protection Agency can subsidize (3) The provisions of Sections 3 (1.1), “drainage interests” at the time the Act larger restoration projects. 3 (2) and 3 (3) of the Nature was being drawn up, especially by the (4) Anyone sustaining a loss as a result of a restoration Protection Act do not apply to agricultural sector. Clear information was project has the right to compensation. measures implemented by the wanted about what restoration would (5) The Minister for the Environment lays down more County Council pursuant to mean for the watercourse of the future. specific regulations concerning restoration projects, subsection (1). A further reason is that the inspiration including regulations concerning the cooperation (4) The Environmental Protection to restore watercourses largely came from between water authorities and between watercourse Agency can subsidize the the USA. In places such as Michigan and authorities and other authorities, as well as on the implementation of measures Wisconsin, efforts had been made to involvement of the public. encompassed by subsection (1). improve habitats for salmonid fish in shallow watercourses resembling Danish PART 6 watercourses (3). The aim of restoration Regulation of watercourses in the USA was – and still is – to further improve fish waters that are already of 16. Regulation of a watercourse is here taken to mean good quality, i.e. to increase the changing the physical characteristics of the watercourse, catchable fish stock. One way of doing so including its course, its width, the height of its bed with was to create artificial overhanging banks respect to Danish Zero Level and its slope, with the excep- using logs that often extended several tion of measures encompassed by Parts 8 or 10. metres into the adjacent terrain. These American experiences were the inspira- 17. Watercourses may only be regulated pursuant to the tion for the wording of the Danish stipulations of the watercourse authority. Watercourse Act, and for the first Danish attempts to rehabilitate watercourses. Apart from these first projects, however, Box 1.2. Provisions Thus in contrast to this approach, reaches, while as far as possible refraining we have not been bound by the of the Danish current Danish philosophy instead favours from building fish ladders. The latter are American examples. Moreover, methods Watercourse Act rehabilitation measures that blend in with considered too selective as they primarily of the type used in the USA introduce pertaining to the natural conditions in the watercourse facilitate the passage of strong salmonids, unnatural “hardware” into watercourses restoration and as simply as possible. For example, we while other fish and macroinvertebrates and are considered undesirable in the regulation. now prefer to restore free passage at are unable to pass. In contrast, a riffle or present Danish view of watercourses. dams by means of riffles and bypass bypass reach can be traversed by all the 8 Introduction fish and macroinvertebrate species 66 633 m from the source 1,123 m from the source 2,387 m from the source inhabiting the watercourse. In addition, 65 riffles and bypass reaches function as a natural part of the watercourse, and in 64 some cases do so better than upstream and downstream reaches (4). 63

62 Regulation as a rehabilitation measure Despite the fact that the five methods 61 mentioned in Part 8 of the Watercourse Height above sea level (m) Act (Box 1.2) are extremely limited, in 60 0123456 0123456 0123456 m practice it has nevertheless been possible to use other and more extensive forms of Figure 1.2. Three Maintenance of Danish watercourses implementation of environmentally sound rehabilitation. All that was needed was to cross-sectional has traditionally served the sole purpose maintenance has led to a four-fold increase obtain approval to regulate the water- profiles of the of holding in check the natural changes in the trout population of county water- course under Part 6 of the Watercourse upper reach of the that take place in watercourses so as courses in less than ten years (6) (Figure Act (Box 1.2). The watercourse regulation river Gudenå. The toensure that the water could drain away 1.3). Environmentally sound maintenance provisions were originally formulated with thin line indicates sufficiently effectively. Thus with has primarily been implemented in the a view to easing water drainage through the profile in 1992, traditional maintenance, one removes county watercourses, and to a lesser deepening, straightening and widening while the thick line vegetation in the watercourse and to extent in the municipal watercourses (7). of the cross-sectional profile. However, indicates the profile some extent on the banks, removes mud rehabilitation also involves changing the as it should be and sand deposits, and removes gravel Environmentally sound watercourse physical form of a watercourse, and from according to the and sand. One works against the natural maintenance the legal point of view is therefore Provisional Order of forces at work in the watercourse, and Watercourse maintenance can be elabo- regulation. It was thus on the basis of 1941 (5). has therefore to repeat maintenance rated to environmentally sound water- provisions on watercourse regulation that regularly to keep the watercourse in check. course maintenance. While traditional Nordjylland County undertook the first With the advent of the new Water- maintenance aims to “repair” the real rehabilitation projects in Denmark in course Act, traditional maintenance of changes that take place in a watercourse, 1980. watercourses has in most cases been environmentally sound watercourse A 1995 amendment to the replaced by more environmentally sound maintenance aims to actively change the Watercourse Act – Section 37a – added a maintenance. With the new practice, one watercourse in order to develop forms new provision to the Part dealing with works with the natural forces in the that make it a well-functioning habitat. rehabilitation (Box 1.2). This provision watercourse by limiting weed clearance, Restoration and environmentally sound enables the County Council to improve by clearing a current channel, and by not maintenance supplement each other. conditions in watercourses in which dredging outside the watercourse’s They both improve physical conditions in summer discharge is poor, for example, stipulated cross-sectional profile. One no watercourses. With environmentally immediately downstream of intakes to longer removes stones and gravel and sound maintenance, one can develop a freshwater fish farms. In such cases, the one does not clear vegetation on the banks. narrow meandering course in a County could limit the amount of water One has still to ensure that the discharge channelized watercourse using the forces diverted to the fish farm by stipulating a capacity stipulated in the Provisional at work within the watercourse. These minimum residual discharge in the Order governing the watercourse is not new meanders primarily lie within the watercourse. diminished, however. There is usually watercourse’s cross-sectional profile and considerable leeway to do so, though, are usually formed in a process dominated Maintenance since the cross-sectional profile of many by deposition in which the aquatic plants It is not just through physical restoration of the watercourses is actually greater become replaced by marsh plants, which that one can improve the condition and than that stipulated (5) (Figure 1.2). eventually merge with the banks. As a form of watercourses. This can also be Environmentally sound maintenance rule, the results are clearly apparent in the achieved through watercourse mainte- can have a markedly beneficial impact on form of a narrow winding course that nance. the watercourse environment. In Funen develops within the course of three years County, it has thus been shown that the or less. 9 Introduction

60 maintenance practice has improved in which the ecological and hydrological County watercourse 1985 1991 physical conditions in thousands of processes function appropriately. 40 kilometres of Danish watercourse during Another way of assessing the need for the same period (7). Thus in the majority rehabilitation is to consider the large of Danish watercourses, good physical number of watercourses that do not yet 20 conditions will have to be ensured by live up to their quality objective. A Danish environmentally sound maintenance. In nationwide survey encompassing more addition, environmentally sound main- than 11,000 watercourse monitoring 0 Municipal watercourse tenance is often a precondition for stations revealed that at two thirds of the fulfilment of the aims of a rehabilitation stations, the watercourse did not comply 40 project. For example, environmentally with the stipulated quality objective (8). sound maintenance can hold sand While one reason for this is continued Percentage of watercourses migration in check so that newly established discharge of sewage effluent, in the vast 20 spawning grounds can function (7). majority of cases poor physical conditions Environmentally sound maintenance is are responsible. Thus, according to this 0 also a precondition if there are to be Danish survey, 26% of watercourses 0-1 1-10 11-20 21-50 51-100 >100 suitable hiding places for the trout fry. under 2 metres in width failed to comply Trout density (No. per 100 m2) Environmentally sound maintenance with their quality objective because of does not enjoy the same public attention hard-handed maintenance and poor as restoration projects. With restoration physical conditions (Table 1.1). Such “deposit-based” meanders often Figure 1.3. In work, the public can see improvement in have difficulty in cutting through the county water- the watercourse from day to day. In Watercourses of natural origin watercourse’s cross-sectional profile and courses on Funen, contrast, the improvements brought about As mentioned earlier, there are approxi- into the adjacent terrain to develop a the trout popula- by environmentally sound maintenance mately 30,000 km of watercourse of natural freely meandering watercourse tion has increased take place gradually over longer periods. natural origin in Denmark (7). These are with erosion-based meanders. Given the in step with the Restoration therefore has an impact over watercourses created by the geological relatively low slope of Danish water- introduction of and above that on the watercourse reach forces of nature. courses, the development of “erosion- environmentally in question, by creating general interest In addition, there is an equivalent based” meanders will take a long time, sound watercourse in the endeavours to improve our water- length of canals and drainage ditches. often 100 years or more. maintenance. In the courses. However, these are only the relics of a With physical restoration, the time municipal water- As mentioned in the introduction, this time when there were even more, many frame is much shorter. Using an excavator courses, in contrast, book primarily focuses on restoration. of the field drains having disappeared one can rapidly excavate new meanders. the trout popula- Thus despite the important role played by again after it became technically and Similarly, one can reopen culverted reaches, tion has remained environmentally sound maintenance, it economically feasible to drain the fields one can remove obstructions and one can sparse, probably will not be discussed further. with drainpipes. No statistics are available lay out new stone and gravel beds in largely due to hard- as to how many kilometres are involved. places where only a sandy bed remains. handed mainte- The need for rehabilitation Typically, though, nearly all the ditches Moreover, when it comes to reopening nance (6). and brooks in cultivated fields will have culverted reaches or restoring free passage When assessing the need for watercourse disappeared into drainpipes because they at obstructions such as weirs and dams, rehabilitation, a first step is to determine were in the way of work in the fields. On there is no alternative to physical how many watercourses are impoverished the other hand, the open ditches and restoration, not even in the long term. in comparison with what one considers to brooks in woods and forests have been Excavators are expensive to run, be a naturally functioning watercourse. left open because tree roots would however. Thus the total length of water- That a watercourse is naturally function- otherwise have rapidly blocked the courses improved over the last 10 years ing does not necessarily mean that it is drainpipes. by remeandering and reopening of untouched. Thus even in the modern On the basis of cartographic studies, culverted reaches in Denmark is estimated landscape, there are watercourses that Brookes (9) has estimated that of the to be less than 100 km – and perhaps have retained their natural functions to 30,000 km of Danish watercourse of even only half of that. In contrast, the such an extent that they serve as good natural origin, only about 900 km have implementation of environmentally sound habitats for a diverse fauna andflora, and retained their natural form. The percent- 10 Introduction

channelized watercourse. This is especially Cause of problem % so during periods of high discharge, when it is natural for the meandering Deposition Pool Poor physical variation due to channelization 15 watercourse to flood its banks. This (mud) Hard-handed maintenance 11 reduces erosion in comparison with what Sewage effluent from sparely built-up areas 27 would occur if discharge of corresponding Sewage works effluent 22 magnitude was forced through a Riffle Loading from agriculture 7 channelized watercourse. Erosion also (gravel) Low water discharge 5 takes place in meandering watercourses, Ochre 5 but the special “corkscrew” form of the Pool Deposition Loading from freshwater fish farms 2 current ensures that the eroded material Miscellaneous 6 is deposited again immediately down- stream of a meander bend. Sand migration is thus considerably less in a meandering age of watercourses that have retained Table 1.1. Reasons watercourse than in a channelized Figure 1.5. A watercourse meander. their natural form varies considerably for noncompliance watercourse. Current, bed and depth conditions follow from county to county (Figure 1.4). It is with quality fixed patterns along a watercourse’s hardly surprising that the greater the objectives for Flooding meanders (7). former drainage intensity in a county, the watercourses under Rehabilitating channelized watercourses lower the percentage of watercourses two metres in width in such a way as to restore a more natural that have retained their natural form. (8). path and enable the watercourse to flood between high and low discharge are less The watercourses have lost their its meadows often has a positive influence pronounced. natural form because of channelization on hydrological conditions in downstream Flooding can also have a local impact. and deepening, and the very hard- reaches. Thus allowing a watercourse to Thus it enhances the capacity of the handed maintenance formerly practised – Figure 1.4. flood its immediate surroundings reduces meadows to denitrify nitrate derived from a maintenance practice that should Percentage of the risk of flooding further downstream, the cultivated fields because the anoxic rightly be called regulation. watercourses having where the consequences can be more zone is greater in a wet meadow. It is common ecological knowledge retained their severe due to the size of the watercourse In addition, flooding can reduce the that the more diverse the environmental natural form shown and the magnitude of discharge. In risk of iron leaching from meadows conditions, the more diverse the fauna for each of the 14 addition, the flooded areas temporarily containing pyrite. With channelized and and flora (10). The uniformity of Danish counties (7). store the water such that oscillations deepened watercourses the groundwater channelized and deepened watercourses, which is maintained by hard-handed Watercourses still having their natural form % Drained (m km-2) maintenance, thus provides poor conditions % of total drained area for life. 60 50 40 30 20 10 0 10 20 30 County (1,000 ha) In contrast, the great physical variation Nordjylland 30 129 in current velocity, depth, bed sub- Viborg 40 109 stratum, vegetation, and bank form that Aarhus 45 136 characterizes naturally meandering Ringkjøbing 34 112 watercourses provides a wide variety of Vejle 48 98 habitats for plants and animals. Ribe 32 67 In a naturally meandering watercourse, Sønderjylland 62 183 the distance between meanders is Funen 55 135 generally approximately 10–14 times the Vestsjælland 78 162 width of the watercourse when full to the Roskilde 57 33 edge (Figure 1.5). This distance is referred Frederiksborg 71 45 to as the meander wavelength. The Storstrøm 80 198 current in a meandering watercourse Copenhagen 64 > affects its bed and sides with forces that are much smaller than in a corresponding Bornholm 60 >22 11 Introduction table sinks in the adjacent fields. As a Figure 1.7. Water- References to Chapter 1 result, a greater area becomes oxic, and courses of Ribe the pyrite present in the soil might be County that were 1 Nielsen, J. (1995): Fish requirements as to watercourse physical condition – A selection washed out as ochre. In some parts of the still closed to of existing knowledge (in Danish with country, ochre contamination has migratory fish in English summary). – Environmental Project effectively precluded the presence of a 1993 (12). No. 293, Danish Environmental Protection diverse watercourse fauna. Agency. 129 pp. Remeandering of a watercourse can 2 Osborne, L.L., Bayley, P.B. & Higler, L.W. thus remedy some of the consequences (eds.) (1993): Lowland stream restoration: Theory and practice. – Freshwater Biology of former channelization and deepening (special issue) 2: 187-342. of the watercourse. Moreover, it can have 3 Hunt, R.L. (1992): Evaluation of trout a positive influence on water quality, not habitat improvement structures in three just in the watercourse itself, but also in considerable efforts to make the high-gradient streams in Wisconsin. other aquatic areas. obstructions passable (Figure 1.7). – Technical Bulletin No. 179, Department of Natural Resources, Madison. 210 pp. Despite the many rehabilitation 4 Nielsen, J. (1994): Fish passage at obstruc- Restoring continuity between projects that have already been under- tions in Danish streams. – Vejle County watercourse reaches taken in Denmark, there still remains a Council. 9 pp. Uniform physical conditions is just one of considerable need to carry out further 5 Hansen, H.O. (in press): Remeandering of a the problems associated with channelized projects in order to achieve the diverse Danish headwater stream: The river Gudenå watercourses. Another is that the water- flora and fauna that we expect in our demonstration project. – Internat. Verein. Limnol. course fauna is often hindered from watercourses. 6 Wiberg-Larsen, P., Petersen, S., Rugaard, T. moving freely upstream and downstream & Geertz-Hansen, P. (1994): Better water- by dams and other obstructions. course maintenance increases the number of Many of the obstructions were fish (in Danish). – Vand & Jord 6: 263-265. established in connection with channeliza- 7 Madsen, B.L. (1995): Danish Watercourses tion, when weirs were built to even out – Ten years with the new Watercourse Act: Collected examples of maintenance and the former gentle fall over the meanders. restoration. – Environmental News No. 11, Right up to the end of the 1970s, closely Danish Environmental Protection Agency. spaced obstructions were common even 206 pp. in relatively small river systems (11) Figure 1.6. Obstruc- 8 Friberg, N., Græsbøll, P. & Larsen, S.E. (in (Figure 1.6). In some places, obstructions tions in the Vegen press): Causes of the generally poor state of smaller Danish watercourses (in Danish). have hindered the free passage of fish for river system late in – Environmental Project, Danish Environmen- centuries. Despite concentrated efforts to the 1970s. The tal Protection Agency. remove the obstructions, considerable obstructions 9 Brookes, A. (1984): Recommendations numbers still remain. An example is Ribe hindered trout in bearing on the sinuosity of Danish stream County, where large areas were still reaching the channels. – Technical Report No. 6, Freshwater Laboratory, Danish Environmen- closed to migratory fish in 1993 despite spawning grounds. tal Protection Agency. 130 pp. 10 Thienemann, A. (1950): Die Verbreitungsgeschichte der Süsswassertierwelt Europas (in German). Obstruction for salmonids – Die Binnengewässer Band XVIII, Stuttgart. Spawning gravel 11 Ansbæk, J., Jensen, F., Schultz, K.E. & Aagaard, P. (1981): The significance of watercourses to society (in Danish). – Freshwater Laboratory, Danish Environ- mental Protection Agency. 12 Ejbye-Ernst, M. (1993): Watercourse fish populations (in Danish). – Ribe County Council, Technical and Environmental Department. 39 pp.

12 2 Mogens Bjørn Nielsen From idea to reality

The present chapter discusses the most . Coupling of interests between land- important considerations, technical owners, the public and the authorities, aspects and legally required approvals and drawing up of the project that are involved when undertaking a . Approvals and processing by the watercourse rehabilitation project in authorities Denmark. As the examples in this book . Clarification of financing illustrate, the purpose of rehabilitation, . Construction – the physical work the solutions, and the interests that have . Assessment and follow-up. to be taken into consideration vary from watercourse reach to watercourse reach. By far the majority of the projects are The chapter examines restoration step undertaken by the Counties and Munici- by step – from the initial idea until palities in collaboration with one or more completion of the project in the field. In other parties. The Counties have drawn addition, a check list is included at the up a policy and strategy in the environ- end of the chapter that Danish authorities ment and nature area, and administer the should find useful when drawing up majority of the laws pertaining to water- projects aimed at improving watercourses courses and the landscape. In addition, and riparian areas. If modified to take many of the Municipalities have plans for local conditions into account, the procedure their watercourses, and in some cases could also be used by the authorities of also have restoration plans. There are also other countries. examples of projects having been under- taken by private interest groups or the Course of a Danish State. rehabilitation project The European Centre for River Restoration at the National Environmental Carrying out a watercourse rehabilitation Research Institute in Silkeborg houses a project in Denmark is often a matter large collection of reports and project requiring patience. The following stages descriptions pertaining to watercourse are normally involved: restoration. There one may obtain inspira- . Initial idea tion and benefit from the experience . Pilot studies gained in earlier projects. In order to be . Contact to landowners and provisional able to expand the collection and build acceptance up a broad European base of information, 13 From idea to reality the Centre is very interested in receiving The fact that restoration can also lead Contact to landowners and project descriptions, assessments and to a more varied nature in the watercourse provisional acceptance other experiences on restoration projects and its immediate surroundings, and Assuming the pilot study or the outline carried out in European countries. thereby to better hunting and fishing, can project does not preclude the project sometimes help tip the balance in favour being undertaken, thereafter follows Initial idea of undertaking such projects. what is often the most important phase. The initial idea for a watercourse restora- Thus beforeproceeding with the project, tion project typically comes from: Pilot studies it is advisable to go over the project idea In order to obtain a first impression of with the landowners involved. The first . Private individuals whether an idea is scientifically defensible, contact should be made personally to each . Groups of landowners a pilot study or an outline project should individual landowner. It is very important . Residents associations be made. Relevant maps should be that the project outline presented to . Interest groups, e.g. angling associa- them is clearly only a proposal. This tions, nature conservation societies, ensures that it will be possible to incorpo- ornithological societies rate local ideas and wishes into the . Municipal Councils, municipal techni- project, something that is only normally cal departments possible provided one is not technically or . County Councils, county landscape politically bound to a particular solution departments, county environmental beforehand. departments. It is inadvisable to arrange and under- take a large public meeting at too early a Over the last few years, the Counties and stage, when the basis for the project is Municipalities have increasingly received too loose and only the basic idea and a enquiries from landowners concerning summary pilot study are available. The restoration of watercourse reaches on democratic rights of parties involved are their property. In some cases, the enquiries assured by the mandatory periods for the have come from residentsassociations. In submission of objections and appeals fact, the question “Couldn’t we have our during the various stages of the approval former meandering stream back in the process (Figure 2.1). Thus the public meadow?” once posed by the residents meeting should not be held until such of Bevtoft in Sønderjylland County was time as one has discussed the project the impetus for one of the first major with the landowners affected and remeandering projects in Denmark – the incorporated some of their ideas and restoration of 2 km of Gelså stream (see The stream Rind acquired, for example showing the comments into the project, but is still open Chapter 5). restoration project. former course prior to channelization, to possible further changes to the project. Marginalization of riparian areas and biological conditions should be investi- The usual outcome is that not all the the fact that an increasing number of gated, various measurements made and wishes and comments can be followed rural properties are being overtaken by soil samples collected. In addition, simultaneously, and the choice between urbanites also increase the possibilities for information on discharge in the water- possible solutions thus becomes a undertaking watercourse restoration course or in the catchment area should political decision. Hence it is normally a projects. Enquiries from established be obtained, larger-sized technical good idea that politicians from the interest groups tend to be somewhat structures in and alongside the water- responsible watercourse authority also more organized, their members often course should be checked, and possible participate in the public meeting. The having a very good knowledge of which legal constraints on the project be involvement of politicians signals to watercourses would benefit from investigated. On this basis, an assessment participants that there is more to the restoration. Ideas also arise in so-called should then be made of whether or not project than just some technicians’ idea. “Regional Countryside Councils” set up the project is technically realistic. The Moreover, one is more likely to accept by the Counties, and in which the results of the pilot study will subsequently solutions arrived at on a political basis “green” organizations are represented be incorporated in the detailed project when one has seen and heard the together with farming organizations, etc. description. politicians in question. 14 From idea to reality

. A greater number of more varied Project proposal habitats for (threatened) plant and animal species . A greater number of more varied dispersal corridors for plants and Comments from other pertinent authorities animals . Reduced ochre loading . Protection of groundwater resources No Initial approval by the Decision announced . Enrichment of outdoor life, including watercourse authority – 4-week appeals period angling and hunting . Compliance with international obliga- Appeal Public announcement tions (conventions, protected of the project wetlands, etc.). – 4-week appeals period Decision by the Danish EPA (With public hearings Appeal – 8 weeks notice) rejected With restoration projects involving remeandering and raising the water- Decision on possible course bed, possible results include: Land Tribunal financial questions – 8-week appeals period (possible compensation) No . A meandering watercourse with Settlement settlement Appeal Possible approval pursuant greater landscape value to the Nature Protection, . Less ochre loading (in cases where

Environmental Protection Land Tribunal Board Appeal accepted there is ochre in the vicinity of the and Water Supply Acts of Appeals watercourse) Watercourse authority announces approval . Wetter meadows with greater nutrient – 4-week appeals period turnover Appeal Final decision by . Greater physical variation in both the the Danish EPA watercourse and the adjacent areas . A greater number of different species of animals and plants . Better recreative possibilities, e.g. Project undertaken Project rejected angling, walking, sailing, bird watch- ing and hunting . Enhanced quality of life. Coupling of interests between land- Figure 2.1. more than just restoring the watercourse owners, the public and the authori- Schematic represen- itself. Thus, riparian areas such as banks When prioritizing possible projects, ties, and drawing up the project tation of the steps and meadows will often also be affected. inclusion of the following considerations Before drawing up the project it is involved in the In some cases, watercourse restoration will help ensure the greatest environmen- important to formulate one or more clear approval of water- involves raising the groundwater table tal and natural return on the investment: objectives. A restoration project can often course regulation and implementing ochre removal. take account of many different environ- and restoration cases The objective when restoring . Ensure that the investments and mental and natural interests, and the by the Danish watercourses and adjacent wetlands changes are permanent wider the proposal is, the more backing it authorities. could be one or more of the following: . Aim for low costs for purchase and will often be possible to obtain. On the construction other hand, though, it is not possible to . Better physical conditions in the . Ensure that there are only few or no take account of all interests at the same watercourse maintenance costs once the project time and place. Priorities have therefore . Enhanced self-purification capacity in has been completed to be established. the watercourse and greater . Take account of several interests A watercourse restoration project denitrification of nitrogen in the wet simultaneously (as described above) comprising restoring the watercourse to meadows . Obtain good political and local its original meandering path involves . A more varied landscape backing. 15 From idea to reality

Watercourse restoration projects often From the legal point of view, the 1. An account of the quality objective for have to be drawn up using a following measures are also watercourse the watercourse and the aim of the multidisciplinary approach involving regulation: proposed restoration project. topics such as: 2. An account of the pilot studies on . Remeandering of a watercourse which the project is based. . Water quality . Various improvements at weirs, 3. An account of the consequences of . Hydrology and discharge including: the restoration project for discharge . Biological conditions Construction of fish ladders and drainage. . Technical installations, such as pipes Split-stream bypass reaches 4. Information on the watercourse’s and cables under and above ground at Rebuilding or removal of weirs/dams present and future form and discharge watercourses, bridges, houses and Reopening of culverted reaches. capacity, and on the associated water other structures, etc. table conditions. . Legal aspects, as described below. The regulations governing how the 5. Information on the planned restoration authorities are to process projects aimed measures and their location in the A new watercource at improving watercourses are stipulated watercourse. being excavated. by the Ministry of Environment and 6. The necessary sketches and maps, Energy in a 1983 Statutory Order. This including an outline plan in a suitable covers both watercourse regulation and scale. watercourse restoration. These regula- 7. A timetable for the work. tions have to be followed by the water- 8. An estimate of construction and course authority in all cases, irrespective running costs. of from where and whom the original idea or initiative for the project derives. If the watercourse authority decides to The approval process is shown proceed with the case, the proposal is schematically in Figure 2.1. laid open to the general public for a Proposals for watercourse regulation period of at least 4 weeks in regulation and restoration are submitted to the cases, and at least 8 weeks in restoration County Council or Municipal Council cases. Announcements are usually made Approvals and processing by the with a view to obtaining the political in the daily press or in local newspapers. authorities decision of the watercourse authority to Landowners and other interested parties Restoration is governed by Part 8 of the proceed with the case. are informed in writing. At the same Danish Watercourse Act (Box 1.2). This time, the proposal is sent to organizations aims to improve a watercourse’s quality The proposal shall include: having the right of complaint (The Danish so that it corresponds to the quality Anglers Federation and the Danish objective for the watercourse stipulated 1. An account of the purpose of the Society for the Conservation of Nature). by the County Council pursuant to the regulation project and a justification of As many projects involve riparian areas in Environmental Protection Act. In addition, the project. the open countryside, it is often also a though, it requires that the watercourse’s 2. The necessary outline maps and good idea to inform the local agricultural drainage capacity should not be affected detailed plans. organizations. The proposal is simultane- to any great extent. 3. A summary of the properties affected ously submitted for hearing at the Developments in the restoration area by the project and a list of landowners relevant authorities, which is always the have overtaken legislation, however, and users who should be involved in County Council, but sometimes the which stems from the early 1980s. Thus, the project. Municipal Council as well. many of the restoration measures in use 4. An estimate of costs including a In all cases, it is required to submit an in the 1990s include elements of proposal for their apportionment. evaluation of the project in relation to the watercourse “regulation” in the form of 5. A timetable for the work. quality objective for the watercourse the remeandering of channelized reaches, stipulated by the County Council and hence are encompassed by Part 6 If the project is undertaken as an actual pursuant to the Environmental Protection Section 16 of the Watercourse Act (Box restoration project, the proposal must Act. The majority of cases also require the 1.2). include the following: approval of the County Council pursuant 16 From idea to reality to the provisions of the Nature Protection Act. With such approvals, there is also a statutory 4-week complaints period. In rare cases, approval is also required from the Ministry of Agriculture and Fishery pursuant to the Freshwater Fishery Act. Thus Section 33 of the Act states that “before permits are issued or decisions reached concerning measures that can affect the passage of fish, fishery and the fish fauna in general, the plans shall be submitted to the Ministry of Agriculture and Fishery for comment”. Due to the often rather complicated legal procedures involved, it is advisable to contact the relevant county authorities in advance to find out what approvals are necessary for the watercourse reach in question and the measures planned. In addition, when drawing up the detailed project it is advisable to evaluate how The river Brede Appeals have a postponing affect such endeavours, and financing often derives comprehensive the impact assessment restoration project. that a project may not be initiated before from a number of sources in the form of studies should be (see below under the the appeal authority has issued a ruling. cash subsidies or labour. In some cases, heading “Evaluation and follow-up”). In these cases, the appeal authority is the labour undertaken by landowners and When agreeing to subsidize larger-sized Danish Environmental Protection Agency. angling clubs is part of the financing. In projects, the Danish Environmental However, in cases where it seems most other cases, land is provided free of Protection Agency will normally require likely that the appeal will be denied, the charge or compensation. that the environmental impact of the Agency can issue approval for initiation of Restoration can sometimes help solve project be documented in some way or construction work. Some appeals are recurring problems with the maintenance other. processed relatively rapidly, while some of a watercourse. Examples are reaches Based on the project proposal and can take several months. which continually silt up or where the whatever comments arise during the With some projects, it is necessary to banks continually collapse, or culverted public hearing phase, the watercourse change the existing ownership conditions reaches where costly replacement of the authority issues final approval for the and property boundaries. The landowners pipes is needed. In such cases, the project. can have an interest in exchanging land, relevant watercourse authority could Before this can be done, however, the for examples if their fields are scattered profitably capitalize future maintenance financial aspects have to be clarified (see rather than being congregated near costs and instead solve the problem by below) and, as mentioned above, thefarmhouse. In addition, it is a legal restoring the watercourse. whatever other approvals might be requirement that property boundaries necessary have to be obtained. and ownership records be corrected The most important additional sources of Thereafter follows a 4-week appeals when a piece of land changes hands. The financing are: period pursuant to the Watercourse Act, most natural would be for the authority . Local sources: Landowners, associa- irrespective of whether the case concerns responsible for the project to take care of tions (residents associations, tourist regulation or restoration. The possibility the task of updating the Land Registry. associations, anglers) and the Munici- of appeals is intended as an emergency pal Council brake in that the watercourse authority’s Financing . Regional sources: County funds for approval should already have taken fully Before the watercourse authority can watercourse restoration, countryside into account the various interests involved issue final approval for a watercourse rehabilitation and management, and and the comments and remarks project, financing has to be clarified. subsidies for specific use of the submitted. Many projects are in effect collaborative riparian areas, e.g. for grazing 17 From idea to reality

. State sources: The Danish Environmen- drainage from the individual landowner’s tal Protection Agency’s funds for property, as well as for future physical Check list watercourse restoration and ochre conditions in the watercourse and for the project description removal, the National Forest and consequently for nature and the Nature Agency’s central pool for environment. In addition, supervision A useful way of arranging a detailed countryside rehabilitation ensures that the funds expended on the project description that complies with . Various funds, firms, companies and work are used in a defensible and legal regulations and requirements private individuals politically approved manner. regarding both regulation and restora- . In a few cases, subsidies for very large The call for tenders only has to be tion projects is as follows: projects have been obtained under the made at the EU level in the case of very EU LIFE programme (e.g. the river large construction projects, i.e. projects Brede, the Skjern river delta, and the where the total construction costs A. Introduction headwaters of the river Gudenå). amount to ECU 5 million or more. . Origin of the idea and location of the area Evaluation and follow-up . Purpose of the project Prior to each individual project, one . Summary of the physical measures should assess how comprehensive the intended specifying exactly what is impact assessment studies should be. In to be done. all cases, follow-up should be undertaken for a period following completion of construction work to ensure that possible damage or undesirable consequences of the project are remedied. In addition, a scientific evaluation of the project by the authority in charge is also necessary. This ensures that valuable experience is gathered for use in future projects. Construction A new stone riffle Another important matter is to reach How extensive this part of the project and two-step agreement concerning maintenance description needs to be depends on the profile. obligations and division of responsibility. extent of the planned construction work. Ideally, this should be clarified in If the watercourse authority decides that connection with approval of the project. the project shall be undertaken by However, from experience we know that contractors, a call for tenders will have to this is not usually done until after be prepared. The call for tenders includes completion of the work. special descriptions of the work which, together with the detailed project, form the basis for the contractor to undertake the construction work. The rules in the Competitive Tendering Act apply in Denmark in connection with the protec- tion of tenders, and it is recommended to seek the advice of persons with a sound knowledge of the Act. An important task is to ensure effective supervision of the construction work. This ensures that the project is undertaken in accordance with the stipulated conditions, dimensions, etc. Among other things, this is important for 18 From idea to reality

B. Description of existing conditions C. Planned measures F. Timetable . General description of the locality (location, . Description of the planned construction . Pilot project terrain, physical conditions, surveys) work suitable for preparing the call for . Preliminary discussions with landowners . Preservation and regional planning con- tenders . Political processing of the project straints, i.e. the Preservation Scheme, . Follow-up work, including re-establishment, application preservation orders and constraints sowing, planting, fencing, bridges and . Possible public hearing stipulated in the County Plan (raw material footpaths. . Public phase reserves, EU Bird Protection Areas, environ- . Final clarification of financing mentally vulnerable agricultural land, etc.) . Necessary approvals additional to those . Land use (cultivation, recreational or other D. Results and consequences under the Watercourse Act, incl. appeal uses) . Expected future conditions, including periods . Fauna and flora (collation of existing water levels, discharge, groundwater . Final approval pursuant to the knowledge/reports and new, conditions, water quality, and flora and Watercourse Act, incl. appeal periods supplementary investigations) fauna . Construction phase . Quality objectives and water quality . Consequences for land use . Follow-up, including updating the Land (recipient quality plan, pollutional state) . Future ownership Registry and deciding future division of . Drainage and discharge conditions (water . Monitoring and impact assessment. maintenance obligations and responsibility. level, discharge, catchment size and character, groundwater conditions, drainage conditions and the provisions E. Necessary permits – summary G. Economic aspects stipulated in the Provisional Order . Pursuant to the Watercourse Act . A precise budget estimate and a summary governing the watercourse) . Pursuant to the Nature Protection Act of financing. . Soil conditions. Information on special . Pursuant to the Freshwater Fishery Act conditions such as soft bed or potentially . Pursuant to the Ochre Act ochreous areas. Valuable information can . From landowners. Review of the property’s H. Annexes often be obtained from existing studies in entry in the Land Registry to determine For a typical major project the following the area. In addition, one should be aware ownership, and to ensure that registered annexes will be relevant: that it is sometimes necessary to undertake rights and easements are not violated. In . Outline maps in scale 1:100,000 and sediment analyses, typically for the heavy addition, easements can reveal information 1:25,000 metals lead, cadmium, mercury and nickel. on the location of technical installations, . Old maps of the area This has to be done if the excavated earth pipes and cables, road rights, etc. When . Survey/survey maps is to be dispersed on agricultural land. The clarifying ownership and agreements with . Planning conditions county authorities have information on landowners, one has also to take into . Existing longitudinal and cross-sectional registered contaminated lands and ochreous account the possible rights of third parties. profiles areas Such rights are not necessarily recorded in . Water discharge, water level, hydrographs . Technical installations, e.g. various cables the Land Registry entry for the property, . Present ownership and pipes (water, sewage, telephone, gas and in agricultural areas will often concern . Present land use and electricity), roads, footpaths and other leasehold agreements. Ask the owner . The measures planned in the project crossings, masts, structures (weirs, dams, about such rights and enter into an . Coming longitudinal and cross-sectional etc.), overflows, inlets, etc. Local utility agreement with the owner that profiles companies and the Municipality’s technical clarifieswho is to cover, for example, a . Miscellaneous detailed drawings department have the relevant information leaseholder’s crop losses caused by . Future ownership . Ownership (private, public, Land Registry construction work. . Future land use. entries, cadastral maps).

19 1 Tøsbæk/Spånbæk brook, Dybvad. Spawning grounds; current concentrators; weed clearance 2 Pump station, Gjøl. Eel pass 3 3 Lerkenfeld stream, Østrup. Examples from Falls ® riffles; spawning grounds the Danish 4 River Storå, Holstebro. Completed watercourse Bypass riffle counties 5 Idom stream, Idum. New course Editor: 6 Rind stream, Herning. Hans Ole Hansen New course; ochre removal rehabilitation projects 7 River Gudenå, Langå. Spawning ground All 14 Danish counties and many of the In this chapter, staff from 12 County 8 Lilleå stream, Hadsten. Falls ® riffles; spawning grounds; municipalities have undertaken a wide Councils describe 24 watercourse bypass riffle; current concentrators variety of different watercourse rehabilita- rehabilitation projects undertaken in 9 Lammebæk brook, Daugård. tion projects over the last decade. These different parts of the country. The Culvert lamellae range from simply laying out large stones, examples provide a good impression of 10 Kvak Møllebæk brook, Skibet. to major projects that remeander water- the variety of solutions and methods Bypass riffle; spawning grounds courses and involve the whole river valley. employed to improve watercourses and 11 River Brede, Løgumkloster. their environment. New course; water table raised; river valley; ochre removal 12 River Brede, Bredebro. Falls ® riffles 13 River Odense at Ejby Mølle, Odense. Falls ® riffles; historical project 24. Jutland 14 River Odense at The Seahorse, Odense. 1 Falls ® riffles; spawning grounds; . historical project .2 Bornholm 15 Lindved stream at Hollufgård, Odense. New course; prehistoric landscape; lakes; sand trap 16 Holmehave brook at Borreby Mill, Odense. .3 New course; spawning grounds; historical project 7 4 17 Esrum stream, Lake Esrum. . ..8 Spawning grounds; current 5. Zealand concentrators; channel narrowing 6 17. 18 Græse stream, Frederikssund. . Falls ® riffles; fish ladder .18 19 Store Vejleå stream, Glostrup. 10 9 New course; removal of paving; .. 19. spawning grounds; current concentrators 20 20 Køge stream, Lellinge. . 21. 14 Sand trap ..13 16 .15 . 23 21 Køge stream, Bjæverskov. . 22 . Riffles; current concentrators 12 11 Funen 22 River Suså at Holløse Mill, Skelby .. Falls ® riffles; historical project 23 Lilleå stream, Kongsted. Reopening culvert/removal of conduits; river valley The geograpical 24 Søbæk brook, Neksø. position of the 24 New course; lakes; sand trap examples described. 21 1 3.1 . Nordjylland County Tøsbæk/Spånbæk

Niels Sloth Jens Berthelsen Hans Heidemann Lassen brook at Dybvad Watercourse system: Voer stream

Introduction to the project Aim of the project shady vegetation. The project outline was In 1976, the Outdoor Council asked passed by the County Council in 1978. Voer stream is a relatively Nordjylland County to participate in large watercourse that flows drawing up a project on ecological Implementation of the project into the Kattegat. Until 1980, watercourse maintenance and re- To undertake the detailed planning of the Tøsbæk/Spånbæk brook, establishment of the fish population in project and coordinate the practical work which is a tributary to Voer the Voer stream watercourse system. The a project group was established com- stream, was a strongly Voer stream system was well suited on prised of a hydraulic engineer and a channelized drainage chan- account of a number of factors: The biologist. In September 1979, the nel with a slight slope of 0.5– water quality had been markedly im- Agricultural Commission approved the 1.5‰ over most of its course. proved, among other reasons because project. Some of the landowners affected Tøsbæk brook was up to 3 major effluent discharges had been appealed the approval decision to the metre wide with uniform stopped, there were no freshwater fish Higher Agricultural Commission, which in weed growth dominated by farms in the system, there were only July 1980 ruled in favour of the project. bur reed. Spånbæk brook minor discharges of untreated urban Restoration work started three months was a 1–2 metre wide harshly sewage, and there were no dams. later and was completed at the end of regulated brook. The water- Moreover, although parts of the main 1993. courses were maintained in course and tributaries were channelized, The restoration work was undertaken accordance with traditional many of the upper parts of the tributaries partly by the County Council’s field practice, i.e. weed clearance were natural with good conditions for the personnel, and partly by a team of young in the whole width of the fauna. unemployed persons as part of a youth watercourse and on the In collaboration with various unemployment project. banks, removal of tree roots government bodies, the County drew up and large stones, and fre- a project outline in 1978 aiming at Impact studies in connection with quent dredging. Because of restoring approx. 3 km of Tøsbæk/ the restoration project the slow flow, the bed of the Spånbæk brook andapprox. 1 km of Voer In 1979, detailed baseline studies were watercourse was comprised stream in order to improve watercourse undertaken encompassing the physical, of fine sediments. quality while maintaining good drainage chemical and biological conditions. In conditions. The measures involved addition, a thorough literature report was included the establishment of current prepared in 1981 based on the current concentrators, gravel banks and pebble international literature on watercourse banks, the establishment of artificial fish ecology and restoration. hiding places, modified and more After restoration work had been environmentally sound maintenance, and completed, thorough studies were made 22 Completed watercourse rehabilitation projects

of sediment deposits. The trees (common The project was one of the first of its alder) have grown up well, and their kind in Denmark, and influenced general roots have now stabilized the banks and, discussion and formulation of watercourse together with the very diverse vegetation, restoration measures for incorporation in provide good hiding places for the fish. the new Watercourse Act of 1982. The The current concentrators, hiding places project is currently a good example of and stone beds in Tøsbæk-Spånbæk how much one can achieve using brook are now virtually invisible as it has environmentally sound maintenance changed its course, while most of those undertaken by well-trained personnel. in Spånbæk brook are still visible and With the aid of environmentally sound functional. The spawning grounds have maintenance and the planting of vegeta- sanded over in some places, while others tion it is in many cases possible to achieve are still visible and usable by salmonids. the same physical diversity as with more The density of the latter is still high, as it substantial measures such as current was already shortly after completion of concentrators, artificial hiding places for the original restoration work. fish and pebble beds. of the impact of the various measures. A Environmentally Project data: report was prepared whose main conclusion sound maintenance was that the environmental quality of the of Tøsbæk/Spånbæk Project organizer: Nordjylland County watercourse reaches had been improved brook Contractor: Nordjylland County considerably without their drainage Project commenced: October 1980 capacity having been detrimentally Project completed: December 1983 affected. The density of salmonid fish has Total costs: DKK 332,000 + studies and administration increased 4–5 fold, and both sea trout (incl. VAT) and brown trout have been noticed Financing: Nordjylland County and Dronninglund and spawning on the gravel banks. Sæby Municipalities In addition, the studies have shown that the gravel banks and current Watercourse data (Tøsbæk/Spånbæk brook and Voer stream): concentrators laid out in the watercourse do not have any major effect on dis- Catchment: 23 and 121 km2 charge capacity, and that environmentally Discharge: sound maintenance considerably Max: 2,280 / 12,100 l s-1 improves watercourse quality. This also Min: 79/436 l s-1 applies to the reaches where changed Quality objective: B1 (Salmonid spawning and nursery waters), maintenance practice is the only measure B2 (Salmonid waters) that has been implemented. Neither does Pollutional class: I, II (1991) environmentally sound maintenance have any negative impact on discharge capacity, Restoration data: which even increased in some reaches where the weed is cleared more frequently. Coordinates: 57° 17´ N10° 23´ E In places where the current channel is Current concentrators: 22 narrow, the bed is rinsed clean of Gravel beds: 14 sediment because of the stronger current. Slope: 0.5 – 3.3‰ Fish hiding places: 45 Experience gained Spawning gravel laid out: 14 beds The watercourse is still maintained in an Stones laid out: 10 beds environmentally sound manner, and there Vegetation: 1,500 trees is still a meandering current channel free 23 3.2 2 Nordjylland . County Pump station at Gjøl

Niels Sloth Jens Berthelsen Hans Heidemann Lassen

Watercourse system: Limfjorden fjord

Introduction to the project Aim of the project distribution well. The other half of the The land drainage pump In 1992, Brovst Municipality approached water runs through a pipe from the station at Gjøl drains water Nordjylland County to enquire about the bottom of the distribution well back to to Limfjorden fjord from an possibilities for establishing a fish pass the inner canal. This water flushes any approx. 12 km2 low-lying between Limfjorden fjord and the young eel that have been guided into the catchment area separated watercourses leading to the pump distribution well into the watercourses. from the fjord by a dyke. station. The County agreed to participate The pipe ends in a trap box containing a Water is pumped from in the project because it seemed likely small elver trap. The pumps and the eel approx. 150 km of drainage that the watercourses would provide a pass function during the period April- ditches and an unknown good habitat for eel to grow and thrive. September, when the eel migrate. number of private and It was estimated that it would be As the system was untried, two pilot -2 -1 municipal watercourses possible to grow 9.3 g eel m yr . When systems were established – one on each estimated to a total of the eel migrated to Limfjorden fjord, they side of the canal that leads the water approx. 200 km. could be caught, for example in eel traps. from the pump station out to the fjord. The area has a very good eel population, but the pump Implementation of the project Impact studies in connection with station completely blocks the The project was initiated in autumn 1992. the restoration project passage of eel and other fish. An outline project for an eel pass was The pumps were started for the first time It has not been possible to drawn up and submitted to the Ministry in April 1993. The trap box was emptied construct an eel pass in the of Agriculture and Fisheries, which once-twice weekly in 1993–94. Elvers usual manner because the approved the project. Brovst Municipality that could pass the trap’s 2 mm mesh net water level inside the dyke is also recommended the project for a were not registered. In 1995, the 2 mm lower than outside. three-year trial period, and an agreement mesh net was therefore replaced by a 1 The organic production of was entered into with the dike owners’ mm mesh net. Four eel were caught in the drainage ditches and association on the establishment of the 1993, all of which probably entered by watercourses leading to the pass. chance, while no eel were caught in pump station is high. In most Water from the lower-lying inner 1994. cases the designated water- pump canals is pumped to a distribution The reason for the poor result is -1 course quality objective is B3 well (500 l min ). From there, half of the probably that the guide current was – ciprinid waters, although water flows out to the outer pump canal insufficiently strong and/or that the the designated quality through a pipe filled with loosely difference in salinity in the area was objective in the upper intertwined plastic strips designed to insufficient to enable the eel to find the reaches of a few watercourses facilitate the passage of eel (see diagram). outer pump canal, which ends in a is B1/B2 – salmonid waters. This water serves as a guide current to brackish area with a high-tide sluice. In enable the young eel to move up to the addition, the sluice was closed for most 24 Completed watercourse rehabilitation projects of the time in summer 1994 due to the dry weather, and hence there was no Project data: connection between the fjord and the canal. Project organizer: Nordjylland County Salinity measurements made at regular Contractor: Nordjylland County intervals have revealed a salinity diffe- Project commenced: 1992 rence of 2–4 ‰ between the water Project completed: 1996 pumped from the inner canal and the Total costs: DKK 40,000 (incl. VAT) water in the outer canal. At one point in Financing: Nordjylland County the summer 1994, the water being pumped out was more saline than the Watercourse data: surface water in the outer canal. This was due to density stratification in the inner Coordinates: 57° 04´ N9° 44´ E canals caused by seepage of salt water Catchment: 12 km2 into the bottom of the canals, from Discharge: where the water was drawn by the pump. Max: 1,200 l s-1 A pump inlet was therefore established in Min: 0 l s-1 fresh surface water. Quality objective: B3 (Cyprinid waters) (B1 Salmonid spawning and Experience gained nursery waters; B2 Salmonid waters) Impact studies have revealed that the eel Pollutional class: II–III (II) (1991) pass does not yet function in the manner envisaged. The trial period will be pro- longed and modifications will be made underway. Fish surveys will be undertaken to determine if eel are in fact present in the outer pump canal, or whether it is the eel pass itself that does not work. In addi- tion, the occurrence of eel inside the dike will be investigated. An alternative to the eel pass could be to release eel directly Cross section of the into the watercourses leading to the pump station at pump station. Limfjorden fjord.

Pipe containing loosely intertwined plastic strips

Distribution well

Elevation 0 Inner canal (elevation -2.6)

Outer pump canal Pipe to the inner pump canal

Trap box 25 3.3 . Viborg County 3 Lerkenfeld stream

Rolf Christiansen at Østrup Watercourse system: Lerkenfeld stream

Introduction to the project Lerkenfeld stream arises in Nordjylland County, from where it runs west into Aim of the project Implementation of the project Limfjorden fjord. The stream As part of their general work on the In December 1993, the two weirs were lies in a narrow valley with clearance of obstructions, Viborg and converted to spawning grounds. As there numerous springs in the Nordjylland Counties are in the process was a risk of ochre washout if the meadows alongside the of dismantling the seven weirs in order upstream water level fell, the spawning whole of the stream. The to improve passage to the upstream grounds were laid out as a carpet with an land adjacent to the reach in reaches that are designated as salmonid even slope such that the top of the bank question has been identified spawning waters. was at the same level as the upper edge as potentially ochreous. The Four of the weirs are located of the former weir. reach was channelized at the immediately downstream of bridges The spawning gravel was laid out over end of the 1950s, at which and other constructions. These weirs a length of 35 metres. Downstream of time seven weirs were were evened out in 1994 by laying out the spawning ground a 10-m long cross- established in the stream. stone mixes, chiefly comprised of large- sectional profile was built up using fist- From the agricultural point sized stones. At one of the other sized stones in order to stabilize the of view channelization was concrete weirs the drop in water level spawning grounds. The profile lies unsuccessful since the ripar- was only 25 cm, and the weir was approx. 15 cm lower than the top of the ian areas were only culti- therefore removed without any form of spawning ground. In order to protect the vated for a few years before reinforcement. No erosion of any banks from erosion during the initial being turned back into importance has since been noted in the period after their establishment, meadow again. reach. spawning gravel was also placed along The reach of the stream is When removing two of the seven the sides of the stream along the relatively deep with a uni- weirs a study was made of whether it spawning grounds. form sandy bottom. Further was possible to build stable riffles and Construction costs for the two downstream there is a spawning grounds just by using the spawning grounds amounted to approx. freshwater fish farm with a different gravel sizes that comprise DKK 100,000 (excl. VAT), which is less fish ladder that has to be spawning gravel. At the same time, the than half of what a more traditional open from October to riffles were to be established in such a solution was estimated to cost. February each year. way as to maintain the previous upstream water level. The following Experience gained only concerns the experience gained in From the stabilization point of view it was that study. expected that the two newly established riffles would undergo considerable 26 Completed watercourse rehabilitation projects

rebedding during high discharge periods. One of the weirs in The winter 1993/94 was particularly wet, Lerkenfeld stream Project data: as was also reflected in discharge in the prior to restoration stream. (left). Project organizer: Viborg County After the winter discharge period, A newly established Contractor(s): Viborg County and Agroplan aps Viborg County re-surveyed one of the riffle (right). Project commenced: December 1993 spawning grounds. It transpired that Project completed: December 1993 there had only been a minor amount of Total costs: DKK 120,000 (excl. VAT) erosion on the lower 25 metres of the Financing: Viborg County, Nordjylland County and spawning ground. The upper 10 metres Danish Environmental Protection Agency was the same as when it had been laid out. This is in accordance with the visual Watercourse data: evaluation of current conditions over the spawning ground. Water velocity Catchment: 85 km2 accelerates over the upper part of the Discharge: spawning grounds and does not reach a Mean: 950 l s-1 velocity high enough to erode the gravel Max (10-year): 6,300 l s-1 until some way down along the spawning Min: 520 l s-1 ground. Quality objective: B1 (Salmonid spawning and nursery waters) / In contrast, the gravel that had been B2 (Salmonid waters) laid along the sides of the stream was Pollutional class: II–III (1992) considerably eroded, forming a new spawning ground approx. 5 metres Restoration data:: downstream of the first, and a pool formed between them. Coordinates: 56° 46´ N9° 30´ E Length: 45 m Width: 8 m Slope: 2‰ Discharge capacity: >6,300 l s-1 Spawning gravel laid out: 110 m3 Stones laid out: 60 m3

27 4 3.4 . Ringkjøbing County River Storå at Holstebro

Per Søby Jensen

Watercourse system: River Storå Aim of the project the turbine outlet to guide the fish to the Because the fish ladder functioned so fish pass. Introduction to the project badly, Ringkjøbing County decided to improve passage past the power station. Impact studies in connection with In 1942, a hydroelectric By establishing a bypass riffle past the the restoration project power station was built at station, virtually all fish species should be After the bypass riffle had been con- Holstebro. The river Storå able to pass the obstruction at the power structed a follow-up group was estab- was dammed in order to station, and thereby ensure the fish free lished to regularly assess how it functions provide electricity to the migration to the upper 2/3 of the Storå and decide on any necessary changes in town’s i This hindered the river system. discharge and the shape of the riffle. The free passage of fish to the follow-up group is comprised of repre- upper 2/3 of the Storå river Implementation of the project sentatives of Holstebro Municipality, system. Although a fish The new fish pass was formed as a 655 Ringkjøbing County and the Inland ladder was built when the metre long looped riffle of stones that Fisheries Laboratory under the Ministry of power station was erected evened out a difference in height of just Agriculture and Fisheries. and had subsequently bbuilt, over 5 metres (see diagram). This ensured The follow-up group initiated an it had onlyr worked to a very a sufficiently low current to allow fish of investigation aimed at determining limited extent. all species to pass thehydroelectric power whether and by what species the bypass The hydroelectric power plant. Six resting pools were also estab- riffle was used, and in particular the station dam completely lished in the bypass riffle and spawning extent to which the passage of fish is prevented the passage of the gravel was laid out on some reaches so dependent on discharge in the riffle, as lavaret, a salmonid fish that that it could also serve as a breeding and well as the effectiveness of the spawning migrates into the river Storå Optimal discharge nursery area for the fish. In addition, a gravel laid out in the riffle. in large numbers to spawn. It for fish passes. bar screen was erected downstream of From the results of the investigation it was quite clear that the can be concluded that the bypass riffle is lavaret was unable to pass used by and can be passed by fish of all the old fish ladder. When the 1,000 l s-1 400 l s-1 Discharge Not determined the species that inhabit the Storå river lavaret migrated up the river not decisive system. Moreover, based on the relatively Storå in November-December large catches of a number of species, in an attempt to reach their Perch Gudgeon Bream Rainbow trout among others 4,695 lavaret, it can be spawning grounds, they Pike Roach Dace River lamprey concluded that all fish that wish to could be seen standing in Salmon Eel Sea lamprey migrate upstream are able to find the large shoals just below the Sea Trout Flounder Tench bypass riffle and use it. A precondition, power station. Steelhead Grayling Trout Lavaret though, is that discharge over the riffle is Ruffe varied periodically in accordance with the requirements of the individual species. 28 Completed watercourse rehabilitation projects

Project data:

Project organizer: Ringkjøbing County Contractor: Danish Land Development Service Project commenced: October 1989 Project completed: December 1989 Total costs: DKK 1,300,000 (incl. VAT) Financing: Danish Environmental Protection Agency (DKK 800,000), Ringkjøbing County (DKK 250,000), Holstebro Municipality (DKK 250,000)

Watercourse data: River Storå 2 Road Catchment: 725 km Discharge: Mean: 8,900 l s-1 Hydroelectric -1 Bar- power station Max: 30,600 l s screen -1 Bar Min: 2,500 l s screen Quality objective: Downstream: B1 (Salmonid spawning and nursery waters) Resting pool Upstream: A (Areas of special scientific interest) Power station lake Pollutional class: I–II

Salmon and grayling have successfully Aerial photograph Restoration data: spawned in the spawning grounds laid and sketch map of out in the riffle, albeit that it has not the bypass riffle at Coordinates: 56° 22´ N8° 38´ E been possible to determine the extent. Holstebro hydro- Total length: 655 m electric power Height difference equalized: 5.3 m Experience gained station. Slope at riffle: 10‰ The new operational practice for the riffle Slope at spawning grounds: 4‰ incorporating varied discharge takes into Number of spawning grounds: 3 @ 20 m account both the requirements of the Number of resting pools: 6 individual species as to discharge and the Piped sections under roads: 29 m changes in the migratory patterns of the Bed width at riffle: 2.75 m various species caused by discharge Stone rubble for riffle: 1,025 m3 conditions in the river Storå. Boulders for current shelters: 980 It is clear that the bar screen erected Spawning gravel: 50 m3 downstream of the turbine outlet is of Discharge Oct-May: 1,000 l s-1 (day and night) great significance in enabling sea trout, Discharge June-Sept: 400 l s-1 (day) lavaret, salmon and steelheads to find the 1,000 l s-1 (night) riffle. The distance between the screen bars should not exceed 20 mm. It is noteworthy that high discharge and operation of the floodgate that apparently partly or completely masks the guide current from the riffle do not have any negative effect on the functioning of the pass. 29 3.5 .5 Ringkjøbing County Idom stream at Idum

Per Søby Jensen Aim of the project visible much more rapidly, but the In 1990, it was decided that 280 metres necessary construction work will in most Watercourse system: of the channelized stream reach should cases be relatively expensive. River Storå be restored to its former meandering stream bed, thereby increasing its length Implementation of the project to 570 metres. Determining the path of the former stream Introduction to the project The idea for the project originated in bed was relatively simple since nearly all the County’s landscape department. The the former meanders and wet areas could Virtually the whole of Idom reach was restored to the original stream be identified on aerial photographs of the stream, which is a tributary path so as to fulfil both aesthetic and area as darker patches in the meadows. A of the river Storå, was placed watercourse quality aims. preliminary path of the former stream under a preservation order in As weed clearance and dredging had was thereafter mapped out at a scale of 1985. In this connection the not been undertaken between the closure 1:4,000. With this map in hand, it was uppermost of a series of of the fish farm in 1985 and the start of thereafter relatively easy to find the exact freshwater fish farms was restoration in 1990, the reach had begun course in the stretch of meadow land. By closed down. A reach down- to meander in the excessively wide probing with an iron spear the original stream of the fish farm had watercourse profile. As a result, a well-defined gravel bed of the former previously been channelized meandering current channel had already stream was found, whereafter the “former” to ensure water drainage started to form and the physical condit- and future stream bed could be staked out. from the fish farm. The reach ions were becoming more varied. In a few The material filling the former stream has not been maintained places, the sand sediment had been varied from 0.5–1 metres in depth, and since 1987. flushed away to expose the underlying was chiefly comprised of organic matter gravel. Thus the conditions that good and a little sand lying above the stable watercourse quality demands with respect gravel bed. to undercut banks, deep pools and The excavated material was mainly shallow gravel riffles could probably have spread out on the adjacent fields as a soil been recreated by letting the reach develop improver or otherwise used to close off on its own. Careful consideration was the completely straight channelized reach therefore given as to whether or not to let in the places where it was crossed by the the forces of nature transform the reach remeandered reach. By refraining from towards an expected acceptable result. filling in the whole of the channelized Artificial In the majority of cases such natural reach, several large and small ponds were ponds restoration of channelized watercourse created that are now of benefit to the reaches is to be preferred from the amphibians, animals and birds inhabiting financial point of view. The disadvantage, the area. though, is that the aesthetic value to the landscape of the watercourse meandering Impact studies in connection with Sketch map of the through the whole stream valley would the restoration project remeandered course be lacking for many decades. By excavating The restoration project was followed up of Idom stream. the former meanders the result becomes by electrofishery surveys at three 100 metre 30 Completed watercourse rehabilitation projects

250 Older trout pollution from the fish farm. The positive fish population than those attained in the 200 Fry (0+) development at station 3 is therefore upstream regulated reach by self-restoration. largely attributable to removal of the The total trout population in the restored 150 impact of the pollution as well as to reach is therefore 3–4-fold greater than significant improvement in the physical could be expected had the reach only 100 conditions as a result of self-cleansing been allowed to undergoself-restoration 50 following cessation of maintenance. At to the same degree as at station 3. In the

No. of trout per 100 m station 2, in contrast, the population longer term, however, it can be expected 0 90 91 92 93 88 89 90 91 92 93 90 91 92 93 tended to remain constant during the same that trout density at the restored and the Non-channelized Remeandered Channelized period, this being due to the fact that the self-restored reaches will eventually be restoration process retarded development the same. stations. Station 1 lies downstream of the Total number of for a period as time was needed for plants Restoration of the stream reach has restored reach and has never been trout present at to recolonize the reach and for the gravel thus both helped improve the trout channelized, while station 2 lies in the three 100 metre beds to be flushed free of sediment. population as a result of the better restored reach and station 3 lies upstream reaches of Idom In 1993, however, the trout population physical conditions, and has doubled the and is still channelized (see the figure). It stream during the at station 2 was considerably greater than length and hence area of the reach should be noted that electrofishery in years 1988–93: at station 3; despite the delay, restoration relative to that of the channelized reach 1990 was undertaken immediately prior to Station 1 – a non- created better physical conditions for the prior to restoration. restoration in October, and that the trout channelized population at station 1 has not been downstream reach; Project data: investigated before 1990. Between 1990 station 2 – the and 1991, the number of trout in the 100 remeandered reach; Project organizer: Ringkjøbing County metre reach at station 1 almost doubled, and station 3 – an Contractor: Ringkjøbing County and has since remained constant at upstream still Project commenced: October 1990 around 225 trout, which corresponds to a channelized reach. Project completed: November 1990 density of approx. 1 trout m-2. This level Total costs: DKK 70,000 (excl. VAT) probably represents the trout carrying Financing: Danish Environmental Protection Agency capacity that the stream has in its non- channelized form. Similarly at station 2, Watercourse data: the trout population has increased from 25 trout in the 100 metre reach in 1989 Catchment: 14 km2 to approx. 225 trout in 1993. At station Discharge: 3, the trout population increased from Mean: 180 l s-1 just under 25 trout in 1990 to just under Max: 580 l s-1 150 trout in 1993. Min: 90 l s-1 At all three stations, a satisfactory Quality objective: A (Areas of special scientific interest) / percentage of fry from natural reproduction B1 (Salmonid spawning and nursery waters) and of older trout from several generations Pollutional class: I–II, I has been attained over the 3-year period. Restoration data: Experience gained The difference that is apparent in the Coordinates: 56° 20´ N8° 30´ E development of the trout population at Length: 280 ® ® 568 m station 2 and station 3 from 1990 to 1992 Width: 4 ® 1 m is chiefly attributable to the development Slope: 3 ® 1.5‰ in physical conditions at the two stations. Meanders: 0 ® 15 The reach at station 3 had been harshly Spawning gravel laid out: 0 m3 maintained until the closure of the fish Stones laid out: 20 farm in 1985, and hence until then had Earth excavated: 500 m3 also been marked by the effects of 31 3.6 Ringkjøbing County .6 Rind stream at Herning

Per Søby Jensen

Watercourse system: River Skjern

Introduction to the project Aim of the project ochre was commissioned at the end of At the beginning of the Because of the ochre problems caused by 1992. 1940s, part of Rind stream the upstream lignite beds, an attempt was The ochre is removed using grass south of Herning was made to design a project that in addition trickling basins alongside parts of the channelized in order to to meeting drainage interests and environ- reach, as well as by leading part of the reclaim meadow land for mental considerations, also minimized the water into six shallow basins excavated cultivation. Together with ochre problem. The aim of the project was nearby, the beds of which have been decades of maintenance this therefore to recreate a more natural, sown with special species of grass able to left the stream as a straight meandering watercourse, and to reduce tolerate being flooded for longer periods. channel with uniform banks the problems caused by ochre. The vegetation in the basins promotes that sloped straight down to oxidation of the dissolved iron and retains an almost horizontal bed Implementation of the project the ochre. comprised chiefly of sand and The channelized reach of Rind stream was In connection with the remeandering mud deposits. previously 1,800 metres long. After the work and the establishment of the ochre 3 It was not only the physical reach had been remeandered, it was removal basins, approx. 35,000 m conditions that inhibited the approx. 500 metres longer. This has material was excavated. This was used to species composition and increased the number of hiding places for fill in the former channelized sections of density in the watercourse, fish, and at the same time, new spawning the reach as well as to level out other however, but also the quality grounds have been laid out. parts of the area. Now that the vegeta- of the water. The first part of the project – the actual tion has grown up, it is no longer The reach in question was remeandering work – was completed at apparent that the countryside has been clearly affected by ochre Sketch map of the the beginning of 1992. The ochre removal modified by man. Moreover, the area has from two upstream former remeandered reach part of the project whereby the forces of become an ideal stopover for migratory lignite beds. As a conse- of Rind stream nature are harnessed to clean the water of birds. quence, pH was low and the iron content of the water N exceeded permitted levels.

Sand trap Shallow grass basins

New course Old course 32 Completed watercourse rehabilitation projects

Impact studies in connection with Aerial photograph Three subsequent analyses have revealed idea and implementation was the great the restoration project of the remeandered a degree of treatment averaging 63% for support for the project among the The impact of the project on the iron reach of Rind dissolved iron and 30% for total-iron. landowners. content of Rind stream has been assessed stream. The relatively low degree of ochre regularly since completion of the plant Experience gained treatment attained in relation to through monthly analyses of the inflow The idea for the project originated with dedicated ochre treatment plants, where and outflow water (total iron, dissolved two landowners who came to the county the degree of treatment can reach 80– iron, pH, temperature and oxygen authorities wanting the stream restored 95%, is largely attributable to the small content). Since operation started in 1992, to its former meandering path. In April volume of the basins and poor flow of the plant has continued to reduce the 1991, the County held the first meeting water into them. iron content of the water in reasonably with the landowners in the area, and in In the construction phase dams were close accordance with what was ex- October the same year, the first part of not established in the main course as it pected. The average degree of treatment the project was initiated. The last part of was expected that flow from the stream over the period October 1993 to Septem- the project – the ochre removal basins – to the basins would gradually increase in ber 1994 has been around 43% for was completed in 1992. The main reason step with colonization of the new dissolved iron and 32% for total-iron. for the relatively short interval between vegetation-free meanders with weed. 33 Completed watercourse rehabilitation projects

The water level was therefore expected to Project data: increase, thereby resulting in more frequent flow of water to the basins. The last three Project organizer: Ringkjøbing County series of measurements indicate that the Contractor: Ringkjøbing County increasing distribution of vegetation has Project commenced: October 1991 in fact had a positive influence on the Project completed: February 1992 degree of ochre treatment. Total costs: DKK 910,000 (excl. VAT) For one thing, the water quality has Financing: Ringkjøbing County watercourse restoration funds increased, and for another, the physical (DKK 520,000); conditions have improved considerably, as Danish Environmental Protection Agency ochre funds is apparent in the form of much more (DKK 390,000) varied conditions with fish hiding places, riffles and pools, gravel bed and good Watercourse data: hydraulic conditions.

Remeandered reach: Ochre removal reach: Catchment: 170 km2 52.4 km2 Discharge: Mean: 2,600 l s-1 900 l s-1 Max: 6,700 l s-1 2,500 l s-1 Min: 550 l s-1 200 l s-1 Quality objective: B2 (Salmonid waters) B2 (Salmonid waters) and F (Watercourses affected by ochre) Pollutional class: II–III II–III, affected by ochre

Restoration data:

Coordinates: 56° 06´ N8° 58´ E

Remeandered reach: Ochre removal reach: Length: 1,020 ® 1,340 m 750 ® 950 m Width: 10–12 ® 6–12 m 4 m ® (2–6 m and 2–40 m) Slope: 0.65 ® 0.55‰ 0.8 ® 0.65‰ Meanders: 0 ® 12 0 ® 14 Number of riffles established:7 Spawning gravel laid out: 115 m3 30 m3 Boulders laid out: 100 Earth excavated/incorporated: 15,000 m3 Stone rubble laid out: 40 m3 Earth excavated: 20,000 m3 Number of shallow pools: 6 Watercourse corridors: 1 Sand traps: 1

34 .7 3.7 Aarhus County River Gudenå at Langå

Ole Helgren

Watercourse system: River Gudenå

Introduction to the project The river Gudenå down- stream of the Silkeborg lakes has been channelized and Aim of the project drawn up in close collaboration with the deepened several times over After several years’ discussion as to local committee of the Danish Society for the last century to facilitate whether salmonids spawned in the main the Conservation of Nature, anglers, local navigation with barges, etc. course of the river Gudenå and whether museums, the Natural History Museum, The last time was in the the physical conditions were suitable, the the municipal authorities, Aarhus and 1930s. Large boulders were decision was made in 1992 to undertake Vejle Counties, and affected landowners. blown up, and smaller stones a pilot project comprising the establish- The project involved establishing two and gravel were excavated to ment of an artificial spawning ground spawning grounds. Over an area of ensure a good navigation approx. 2 km upstream of Langå. approx. 1,200 m2 the spawning grounds channel. With the construc- The idea was to re-establish one of the were built up to a height of approx. 1.4 tion of a hydroelectric power former excavated spawning grounds. metres above the existing river bed on a station at Tange in 1921 the However, all such sites proved to coincide base of unsorted stony material covered remaining natural spawning with areas of historical interest (fords, with an at least 40 cm thick layer of grounds in the lower reaches etc.) and it was therefore decided to spawning substrate. The latter is of the river Gudenå establish a spawning ground from scratch comprised of naturally occurring stony disappeared, and the formerly at an otherwise suitable site. material from the area having the so rich salmon populations The final location was chosen from following size distribution: 15% 8–16 died out. among 10 possibilities after numerous mm, 35% 16–32 mm, 35% 32–64 mm investigations of water velocity, profile and 15% 64–120 mm. changes, bottom substratum and benthic The water depth over the spawning fauna. Close examination of the historical grounds is at least 40 cm. Along the aspects also played a decisive role in southern bank of the river there is an at making the final choice. least 5 metre wide and 1 metre deep navigation channel. Numerous large Implementation of the project stones have since been placed in the river The Environmental Division of Aarhus to protect the banks and provide shelter County was given the task of planning from the current. and undertaking the project. In order to The project was undertaken by a ensure that all ideas and viewpoints were contractor during a 14-day period in taken into consideration, the project was autumn 1993. 35 Completed watercourse rehabilitation projects

The physical and hydraulic conditions still fulfil those assumed in the project. Fish were observed spawning at the spawning grounds immediately after completion of construction work in October and for the remainder of the year 1993, and electrofishery in the early summer 1994 led to the catch of the first salmon fry (1 indiv.). Electrofishery and the biological investigations were continued in 1994–95. Experiments involving the laying out of hatching boxes are also planned. In winter 1994–95, the spawning grounds was expanded with an associated shallow-water area designed to provide better hiding places for the fry.

Impact studies in connection with Laying out the the restoration project spawning gravel. Project data: As the project was intended as a source of inspiration for future work on improv- Project organizer: Gudenå Committee ing the environmental quality of the river Contractor: Aarhus County, Environmental Division Gudenå, a number of studies were Project commenced: September 1993 undertaken before and after carrying out Project completed: October 1993 the project: Total costs: DKK 130,000 (incl. VAT) Financing: Gudenå Committee .Pre-, during and post-construction surveys Watercourse data: .Pre- and post-construction measure- ments of discharge Catchment: 1,850 km2 .Pre-construction geotechnical surveys Discharge: of river bed conditions Mean: 22,000 l s-1 .Diver surveys to register aspects of Max: 65,000 l s-1 historical interest Min: 10,000 l s-1 .Pre and post construction investigation Quality objective: B2 (Salmonid waters) of the flora and benthic fauna Pollutional class: II (1993) .Regular electrofishery .Visual registration of fish at the Restoration data: spawning grounds Coordinates: 56° 23´ N 9° 55´ E Experience gained Length: 70 m The accessibility of the selected sites Width: 30 m considerably affects construction costs. In Slope: Average 10‰ the case of the present project, which Discharge capacity: 35,000 l s-1 cost DKK 130,000, road access for the Spawning gravel laid out: 180 m3 delivery of materials was particularly Stones laid out: 90 m3 good. Rubble laid out: 370 m3 36 8 3.8 . Aarhus County Lilleå stream at Hadsten

Ole Helgren Aim of the project The construction of a 12–18 metre wide Watercourse system: Due to repeated flooding of agricultural two-step profile along 4 km stream was River Gudenå land in the 1980s and because the undertaken in 1989 in close cooperation watercourse quality objectives were not with the landowners. The project was fulfilled, the decision was made to do partly paid for by the landowners, who something about the problem. provided the land free of charge, and Introduction to the project The passage of migratory fish was also partly by the Municipalities and the included since approximately half of the County subsidized by the Danish Environ- Lilleå stream, which arises salmonids that migrate up the Gudenå mental Protection Agency. Free passage approx. 20 km west of river system enter Lilleå stream. of fish was ensured by: Aarhus and flows into the The task involved improving the . Replacing the fish ladder at Løjstrup in river Gudenå at Langå, is one stream’s discharge capacity and hence 1988 (cost approx. DKK 200,000) of the river’s main tributaries. drainage safety, while at the same time . Removing the dam at Hadsten Mill and The surrounding landscape enhancing its environmental quality and establishing a riffle in 1989 (cost varies from very hilly to flat ensuring free passage for fish in Lilleå approx. DKK 700,000) plains, although there is a stream and subsequently in the whole of . Removing the dam at Grundfør Mill clearly defined river valley. the Lilleå watercourse system. and establishing a riffle in 1990 (cost Approx. 2/3 of Lilleå stream approx. DKK 450,000) has been channelized over Implementation of the project . Establishing a riffle at Granslev in 1991 the years to meet the needs The complete project was drawn up by a (cost DKK 30,000) of agriculture. As a result of working group involving the landowners, . Establishing a bypass riffle at Voer Mill channelization and marked interest groups, weir owners, municipal in 1992 (cost DKK 130,000) urban and industrial growth, and county authorities. The project took . Removing the dam at Selling Mill and Lilleå stream appeared as a approximately five years to complete and establishing a riffle in 1993 (cost DKK barren watercourse charac- encompassed: 60,000). terized by harsh maintenance and sand migration. Water . Constructing a two-step profile along With the prior agreement of the land- quality was affected by 4 km of the stream owners, interest groups and the authorities, effluent, and discharge was . Replacing a fish ladder each sub-project was administratively very variable, often leading . Removing two dams and constructing processed by the County and subsequently to major flooding. riffles undertaken under contract under the . Constructing a bypass riffle County’s supervision or by the County . Laying out approx. 3,000 m3 stones itself. . Laying out approx. 300 m3 spawning Subsequent to the project, work has gravel been undertaken in the tributaries to . Planting approx. 13,000 trees Lilleå stream whereby one bypass riffle . Drawing up new regulations and has been constructed and two dams switching to environmentally sound removed. In addition, most maintenance maintenance. is now undertaken in an environmentally sound manner. 37 Completed watercourse rehabilitation projects

The course of the project and the The result is a pleasant watercourse methodological manner in which it was with a rich flora and fauna, a green carried out has led to a wide understan- corridor through the stream valley, and ding of the complex problems that often satisfied citizens, landowners, organizations arise when balancing agricultural and and authorities. environmental interests, and has given The course of events and the result rise to a good climate of cooperation have generated considerable goodwill in between the landowners, the organizations the whole catchment area and, among and the authorities. other things, has led other landowners to approach the County with proposals for further improvements to the environment.

Laying out stones in Project data: Impact studies in connection with a two-step profile. the restoration project Project organizer: Aarhus County Studies made prior to the project had Contractor(s): Aarhus County and revealed an impoverished aquatic envi- Danish Land Development Service ronment characterized by few plant Project commenced: 1987 species and a barren sandy bed with a Project completed: 1993 small population of stock fish and only a Total costs: DKK 2,700,000 (incl. VAT) few migratory fish. Moreover, large areas Financing: Danish Environmental Protection Agency of agricultural land were frequently (DKK 350,000), flooded. Following completion of the Hadsten and Hinnerup Municipalities project, sand migration has minimized, (DKK 770,000), and long stretches can now be found diverse landowners (DKK 750,000), having a stony or gravel bed. The species and Aarhus County (DKK 830,000) composition of the weed has changed considerably, and there is currently a Watercourse data: good population of indigenous fish. In addition, migratory fish can now be Catchment: 310 km2 found in nearly the whole of the river Discharge: system. Mean: 2,914 l s-1 Flooding of agricultural land has only Max: 26,000 l s-1 taken place in the spring of 1994, and Min: 720 l s-1 the newly created green corridor has Quality objective: A (Areas of special scientific interest), provided a good habitat for fauna and B1 (Salmonid spawning and nursery waters); flora. B2 (Salmonid waters) Pollutional class: II (Average, 1993) Experience gained The procedure chosen involving a broadly Restoration data: based working group and numerous meetings and public hearings is protracted Coordinates: 56° 19´ N10° 03´ E and resource demanding. However, the Length: 31,200 m subsequent implementation phase is Width: 1–7 ® 1–4 m correspondingly quicker and more problem Slope: 1.1‰ free. Discharge capacity: 26,000 l s-1 The construction work was undertaken Spawning gravel laid out: 300 m3 at times that were favourable for both Stones laid out: 3,000 m3 landowners and the environment. Earth excavated: 35,000 m3

38 3.9 Vejle County .9 Lammebæk brook

Tony Bygballe Jan Nielsen at Daugård Watercourse system: Rohden stream

Introduction to the project Lammebæk brook is a tributary of Rohden stream, Aim of the project At the same time, another culvert which runs through a river The culvert was previously an effective located approx. 500 metres upstream was valley covered with trees. obstruction for migratory fish. Because altered such that there is now free Lammebæk brook falls 40 of the culvert’s 30‰ slope, the water passage to fish along the whole length of metres over a 4 km long level inside was so low and the current the watercourse. reach. It has not been velocity so high that not even strong fish dredged or maintained for like the sea trout were able to swim Impact studies in connection with several years. As a result, it upstream through the culvert. The the restoration project has developed a natural and project aimed to effectively improve the Two weeks after the lamellae had been varied course that alternates possibility for fish to migrate upstream in mounted, sea trout had swum through between small falls, riffles the brook. the culvert and further on up the brook. and deep pools. At Daugård, The fish are now evenly distributed along the brook runs under a main Implementation of the project the whole length of the brook. In 1993, road through a 25 metres The County constructed a simple but there was a fine natural trout population long concrete culvert. effective lamallae-like insert to mount of approx. 2.2 trout m-2. Up to 1994, inside the culvert so as to create refuge 2,000 trout fry were stocked in and resting places for fish attempting to Lammebæk brook each year. However, migrate upstream in the brook. The stocking was ceased after 1994 as the insert is comprised of a wooden plank population is now self-reproducing. with a notch cut on the upper edge of alternate sides, and is fitted to an iron Experience gained bracket having the same form as the Culverts that lead watercourses under culvert. The inserts are mounted on the roads are one of the most common base of the culvert at 2 metre intervals obstructions in smaller Danish water- angled in the direction of the current. courses. If there is insufficient water in The water level at each of these lamellae- the culvert, or if the current is too strong, like inserts was thereby raised at least 30 the culvert forms an effective obstruction cm, andtrout and other fish can now for even the strongest swimmers such a swim through the notches in the sea trout. If the culverts lie deep below lamellae and rest in the basins between the road surface it is often economically them. unfeasible to alter them. Mounting 39 Completed watercourse rehabilitation projects

lamellae in culverts has proved to be a The road culvert very effective means of raising the water before and after Project data: level and reducing current velocity. mounting the Moreover, it is a relatively cheap solution lamellae. Project organizer: Vejle County for a major problem. Contractor: Vejle County Project commenced: October 1992 Project completed: October 1992 Total costs: DKK 18,000 (incl. VAT) Financing: Vejle County

Watercourse data:

Catchment: 5 km2 Discharge: Mean: 75 l s-1 Max: 2,000 l s-1 Min: 25 l s-1 Quality objective: B1 (Salmonid spawning and nursery waters) Pollutional class: I

Restoration data:

Coordinates: 55° 44´ N9° 43´ E Length: 25 m Diameter: 1.25 m Slope: 30‰ Culvert discharge capacity: 6,000 ® 5,000 l s-1 40 3.10 Vejle County .10 Kvak Møllebæk brook

Tonny Bygballe Jan Nielsen at Skibet Watercourse system: River Vejle

Aim of the project down to the river Vejle was undertaken in The aim of the project was to construct a October 1992, and included planting the Introduction to the project bypass riffle around the old watermill adjacent land with common alder. dam in order to restore free passage for Kvak Møllebæk brook is a the brook fauna and at the same time tributary of the river Vejle reduce sand deposition in the millpond. Impact studies in connection with lying approx. 7 km upstream In addition, the channelized and deep- the restoration project of Vejle Fjord. At Kvak Mill, a ened brook downstream of the dam was Subsequent studies have shown that water-driven grain mill built to be remeandered to give it a more many trout were already present in the in the last century, a 4.3 natural course before its outlet into the bypass riffle one month after its comple- metres high dam prevented river Vejle. tion. At that time, trout density was up to the passage of fish. 1 trout m-2. The following year, trout Implementation of the project density in the bypass was 2 trout m-2, the The bypass riffle was constructed in May– trout having started to spawn in the June 1991. Remeandering of the reach bypass itself. There were far more trout in

Bypass riffle at Kvak Watermill. 41 Completed watercourse rehabilitation projects

Project data:

Project organizer: Vejle County Contractor(s): Danish Land Development Service and Vejle County Project commenced: May 1991 Project completed: October 1992 Total costs: DKK 252,000 (excl. VAT) Financing: Vejle County, Danish Environmental Protection Agency and Vejle Municipality

Watercourse data:

Catchment: 4.8 km2 Discharge: Mean: 72 l s-1 Max: 136 l s-1 Min: 36 l s-1 the bypass than in the upstream and Electrofishery in the Quality objective: B1 (Salmonid spawning and nursery waters) downstream reaches of the brook. remeandered reach Pollutional class: I–II Moreover, studies undertaken during of Kvak Møllebæk the sea trout spawning season have brook. Restoration data: shown that numerous sea trout now migrate upstream of the millpond to Coordinates: 55° 43´ N9° 27´ E spawn in the brook’s upper reaches. Thus many more trout are now present in the Remeandered reach: Bypass riffle: brook than previously, and trout stocking Length: 150 ® 190 m 0 ® 260 m has now been stopped. Furthermore, in Width: 3–4 ® 0.6–3 m 0 ® 0.5–1.3 m the remeandered reach twelve spawning Slope: 0 ® 4–5‰ 0 ® 5–25‰ grounds were laid out and sea trout started to use them just a few days after Discharge capacity: Max 150 l s-1 completion of the project. In 1993, there Meanders: 9 was a fine natural trout population of Spawning gravel laid out: 60 m3 approx. 1 trout m-2. Stones laid out: 70 m3 Earth excavated: 200 m3

42 3.11 Sønderjylland 11 . County River Brede

Bodil Deen Petersen Mogens Bjørn Nielsen at Løgumkloster Watercourse system: River Brede

Introduction to the project At Løgumkloster the river Brede runs in a well-defined and rather narrow river valley, the majority of which Aim of the project reach was converted to a 3,130 metre is permanently grass-covered. There were several reasons for wanting to meandering reach and the river bed was From there the river continues restore this particular reach of the river raised. The weir was removed and two past Bredebro, eventually to Brede. Firstly, to improve environmental long riffles were established instead. run out into the Wadden Sea. conditions in the river, including reducing Spawning grounds and stones were laid The river Brede originally the destructive migration of sand. out, and some of the meanders were followed a very meandering Secondly, to remove the last major weir in reinforced with stones. path, but was channelized in the river Brede, thereby enabling the The meandering course is now almost the mid 1950s. The river has upstream migration of salmonids, identical to that prior to channelization since eroded deep down into especially the rare salmonid, the houting, except alongside Løgumkloster town, the landscape and caused which is once again found in the majority where remeandering was not possible considerable sand migration. of watercourses in southern Jutland because a sewer and houses have since Only in very few parts of the courtesy of a successful breeding pro- been constructed at the former course of river there was an actual gramme. The plan also encompassed the river. gravel-bedded current channel improving the continuity between the In several places the former meanders and spawning grounds river and adjoining meadows by raising were preserved after channelization. They suitable for salmonid fish. In the river bed. were still present as open ponds in the 1990, a large weir at Bredebro Prior to the project, the latter lay up to meadows, but became incorporated in was rendered passable by 1 metre below the level stipulated in the the new meandering watercourse after converting it to a riffle (see Provisional Order governing the restoration. To replace them, two new example 3.12). This was the watercourse. The whole of the river valley ponds were excavated in the former only downstream obstruction is potentially ochreous, and raisingthe channelized reach. During excavation in the river system. river bed and hence the water table in work it transpired that one of the former the river valley was also expected to meanders had been used as a landfill, reduce ochre input to the river. and over 200 tonnes material had therefore to be transported to a control- Implementation of the project led landfill. The project was undertaken in the second The project was completed in May 1992. half of 1991. A 2,680 metre channelized 43 Completed watercourse rehabilitation projects

Impact studies in connection with The river Brede near developed, the banks being steep and Compared with the former channelized the restoration project Løgumkloster having been reinforced with fascines. reach the new reach has a greater The plants and benthic macroinverte- during restoration After restoration, the bank vegetation has number of benthic macroinvertebrate brates in the reach in question were in October 1992. become more diverse and well developed. species and the density of macroinverte- studied prior to restoration (in 1991) and The new meanders The vegetation in the river itself was brates is generally greater now because again after six and eighteen months, have been dug and previously strongly dominated by the river bed has become less uniform respectively (in 1992 and 1993). In the former filamentous leaves of the bur reed than previously. addition, electrofishery is undertaken channelized path (Sparganium Emersum), but after Electrofishery has shown that each year in much of the river Brede in has not yet been restoration, there is a higher frequency of numerous and large sea trout migrate up collaboration with the local angling filled in. more environmentally beneficial species the river Brede, and that the houting is association. such as the water starwort (Callitriche now found far up the river system. It has Prior to restoration, the bank vegeta- platycarpa) and the large-flowered water not yet been shown to spawn in the river, tion in the channelized reach was poorly crowfoot (Batrachium peltatum). though. 44 Completed watercourse rehabilitation projects

Experience gained The project affected a total of 10 private Project data: landowners as well as Løgumkloster Municipality. All the landowners were Project organizer: Sønderjylland County involved in the project at an early point so Contractor: Sønderjylland County that they had the opportunity to influ- Project commenced: July 1991 ence the project. They were regularly kept Project completed: December 1991 informed during the whole course of Total costs: DKK 1,750,000 (excl. VAT) events. Financing: Danish Environmental Protection Agency, In 1994 and 1995, a further 6 km of Løgumkloster Municipality and the river Brede downstream of the above Sønderjylland County mentioned reach was restored in the same manner. This project was under- Watercourse data: taken under the EU Life Programme in connection with similar projects in Catchment: 258 km2 England. The significance of the project Discharge: for the river and river valley is still being Mean: 2,700 l s-1 thoroughly investigated by Sønderjylland Max: 16,000 l s-1 County in collaboration with the National Min: 1,000 l s-1 Environmental Research Institute. It is Quality objective: B2 (Salmonid waters) planned to continue restoration of the Pollutional class: II (1990–91) river Brede both downstream and upstream, as well as to undertake Restoration data: projects in some of its tributaries aimed at reducing loading by ochre. The reme- Coordinates: 55° 04´ N8° 58´ E andering project is the largest of its kind Length: 2,680 ® 3,130 m so far undertaken in Denmark. Width (bed): 6 m Slope: 0.3‰ Discharge capacity: 12,000 l s-1 Meanders: 0 ® 13 Spawning gravel laid out: 300 m3 Stones laid out: 5,750 m3 Earth excavated: 48,200 m3

Pilot studies:

Soil analyses in the river valley Surveyance of the river and river valley Collection of water discharge data for the latest years Plants and macroinvertebrates in the river Information on cables and conduits in the area (electricity, telephone, water, sewage, gas) Information on other restrictions and plans for the area (County Plan, Municipal Plan, zoning restrictions, preservation orders, etc.)

45 3.12 Sønderjylland 12 . County River Brede

Bodil Deen Petersen Mogens Bjørn Nielsen at Bredebro Watercourse system: River Brede

Introduction to the project In connection with the channelization and regula- Aim of the project created with an average slope of 5‰. The tion of the river Brede in the The quality objective designated for the riffle is comprised of three sub-riffles with mid 1950s, two large con- majority of the watercourse system a total length of 110 metres. The three crete weirs were built in the upstream of the weir (294 km2) is sub-riffles each have a slope of 10‰ and lower reaches of the water- salmonid waters or salmonid spawning a bed width of 4 metres as compared course system. The weir at and nursery waters. These quality objec- with 6 metres in the parts between the Bredebro was the furthest tives were not fulfilled, partly because of sub-riffles. This arrangement creates two downstream, and with an 8.4 the obstruction caused by the weir. The resting pools between the three sub- metre wide spillway was also aim of the project was therefore to riffles. Downstream of the riffle spawning the largest. The water drop restore free passage for migratory fish grounds have been established for trout over the edge of the weir and thereby render possible the fulfilment and salmon. was up to 1.2 metres during of the quality objectives upstream of the When undertaking the project care the summer period and an weir. This would also increase the area of was taken to ensure that drainage average of 0.6 metre in the watercourse available to the threatened conditions upstream and downstream of winter months. It was there- salmonid species, the houting, which, the riffle were not changed, there being fore a very effective hin- among other places, has been stocked in major agricultural interests in the drance to the migration of the river Brede. intensively cultivated surrounding area. fish up the river. Removal of the weir at Bredebro and the restoration of free passage to fauna Impact studies in connection with was also a precondition for being able to the restoration project restore and remeander the river Brede at Electrofishery is undertaken each year in Løgumkloster further upstream in the the river Brede in collaboration with the system (see example 3.11). In connection local angling association. This has shown with that project, the other large weir in that large numbers of trout now migrate the river Brede was removed. up the river, as do houting and salmon.

Implementation of the project The project was undertaken in late summer 1990. The original concrete weir was not altered. Immediately downstream of the weir, a 250 metre long riffle was 46 Completed watercourse rehabilitation projects

Project data:

Project organizer: Sønderjylland County Contractor: Sønderjylland County Project commenced: September 1990 Project completed: October 1990 Total costs: DKK 550,000 (excl. VAT) Financing: Sønderjylland County and Danish Environmental Protection Agency

Watercourse data:

Catchment: 294 km2 Discharge: Mean: 3,500 l s-1 The weir at Bredebro prior to and following conversion to a riffle. Max: 30,000 l s-1 Min: 1,000 l s-1 Quality objective: B2 (Salmonid waters) Pollutional class: II (1991–92)

Restoration data:

Coordinates: 55° 03´ N8° 51´ E Width (bed): 4–6 m Slope: 5‰ Discharge capacity: 30,000 l s-1 Spawning gravel laid out: 150 m3 Stones laid out: 1,500 m3

47 .13 3.13 Funen County River Odense

Ann Fuglsang Annette Sode Claes Levin Pedersen at Ejby Mølle, Odense Watercourse system: River Odense

Aim of the project Downstream of the floodgate, the riffle Introduction to the project The aim of the project was to restore free was established in the full width of the passage for fish and macroinvertebrates river (approx. 23 metres) for a length of The river Odense is the past the mill dam at Ejby Mølle. 99 metres. As resting basins are incor- largest and most important The water level upstream of the mill porated in the riffle, the average slope is watercourse on Funen. It has had to be preserved unchanged and it 8‰ and the maximum slope 12‰. At the a total length of 54 km and had still to be possible to lead water to average minimum discharge (870 l s-1), with its 631 km2 catchment the mill. the riffle’s run-in profile is fully charged. area with many valuable At higher discharge, the excess water will tributaries drains approx. 1/5 Implementation of the project spill over the edge of the sheet piling wall of the total area of Funen. The work began in June 1992 and was and down into the riffle. The 166 metre Since the 13th century, there carried out in collaboration with Odense spillway can thereby drain away approx. has been a water mill at Ejby Municipality. 25,000 l s-1 before the water level reaches Mølle. The 2 metre high The project was undertaken by flood levels. By regulating the weir at the millpond dam effectively constructing a 166 metre fauna-passable floodgate it is possible to drain away a obstructed all upstream stone riffle upstream and through the total of approx. 45,000 l s-1. migration of fish to approx. floodgate. Downstream of the latter it When discharge exceeds the average 85% of the river’s catchment continues as a further 99 metre riffle. minimum, a small quantity of water can area. Above the former floodgate, a 166 be led to the mill channel, although metre long sheet piling wall has been ensuring that the guide current from the Sketch map of the driven into the bed parallel to the bank fauna passage is always strongest. In fauna pass at Ejby such that a 7 metre wide stone riffle connection with the project a sewer had Mølle (Scale approx. could be established between the sheet to be relaid and an overflow conduit 1:2,000). piling wall and the adjacent bank. moved.

N Mill pond Impact studies in connection with the restoration project Since completion of the riffle, electro- fishery has been undertaken 4 times in Sheet piling wall Floodgate winter 1992–93 in order to determine Entrance to whether the riffle ensures the upstream fauna pass migration of sea trout. In addition, the macroinvertebrate fauna in the lower part of the riffle has Road been studied before and after completion 48 Completed watercourse rehabilitation projects

Project data:

Project organizer: Funen County Contractor: Carl Bro Ltd. Project commenced: June 1992 Project completed: Winter 1992/spring 1993 Total costs: DKK 5,290,000 (excl. VAT) Financing: Funen County, Odense Municipality and Danish Environmental Protection Agency

Watercourse data:

Catchment: 631 km2 Discharge: Riffle and spillway Mean: 5,360 l s-1 viewed facing Max: 36,500 l s-1 upstream from the Min: 250 l s-1 floodgate. Quality objective: B1 (Salmonid spawning and nursery waters) Pollutional class: II and II–III (1993)

Restoration data:

Coordinates: 55° 24´ N10° 25´ E Length: 265 m Width: 7–23 m Slope: 6–12‰ Discharge capacity: 45,000 l s-1 Earth incorporated: 4,680 m3 Stones laid out: 3,290 m3 Earth excavated: 7,540 m3 Piling inserted: 1,227 m2

of the project. A riffle that was present The riffle and The results of the studies have not yet capacity to cope with the levels of there prior to the project was removed in floodgate viewed been reported, but some experience with discharge seen in the river. connection with the establishment of the facing upstream the fauna passage has already been newriffle. The analyses have been from the lowermost gained. The future undertaken since 1989 and involve two resting basin. The project should be viewed in the annual fauna samples. The analysis series Experience gained context of the plan for the river Odense makes it possible to assess how rapidly The riffle at Ejby Mølle ensures satisfac- up to the year 2000 whereby Funen macroinvertebrates colonize the newly tory passage for sea trout migrating County, in collaboration with the Munici- established riffle. upstream. The hydraulic measurements palities and trade and industry, intends to After completion of the project, made after completion of the project develop the Odense river system into hydraulic measurements and calculations show that the calculations on which the European top-class trout waters. have been undertaken in the riffle to project was based held true. The new verify the calculations on which the riffle has proved stable in its construction project was based. and, as predicted, has the sufficient 49 14. 3.14 Funen County River Odense at

Ann Fuglsang Annette Sode Claes Levin Pedersen The Seahorse, Odense Watercourse system: River Odense Aim of the project pality and the County comprising the Introduction to the project The aim of the project was to recreate establishment of a stone riffle and two At Munke Mose in the centre free passage for fish and fauna past the spawning grounds downstream of the of odense, the river Odense solid spillways downstream of “The two solid spillways near The Seahorse. runs through public parkland Seahorse”, and at the same time improve The work commenced in autumn 1993 where a sculpture called “The thespawning possibilities for salmonid and was completed in spring 1994. A Seahorse“ stands in the river. fish in the river Odense. The water level 115 metre long riffle of stones was It is known that Knuds was to be preserved largely unaltered established over the full width of the river Kloster monastery had a between the spillways and the sluice downstream of the southernmost water mill there in 1175. The bridge, as well as upstream of the sluice spillway (see sketch map). water mill no longer exists, bridge. The slope of the riffle varied between but the dam and sluice 5‰ and 12‰. The riffle was completed bridge have been preserved. Implementation of the project with a 25 metre long spawning ground. In order to safeguard the In spring 1993, Odense Municipality In addition, a 40 metre long spawning water level at The Seahorse Sketch map of the approached Funen County with a ground was laid out 75 metre further approximately 70 metres riffle and spawning proposal for establishing spawning downstream. Both spawning grounds downstream of the sluice grounds (scale grounds in the river Odense. The result were laid across the whole width of the bridge, two solid spillways approx. 1:2,200). was a joint project between the Munici- river and sloped 5–6‰. had been established at a point further downstream where the river divides Road around an island. These created a 1 metre high falls Remaining spillway that obstructed effective upstream passage of fish and Riffle fauna to 85% of the river’s catchment area. The Seahorse Riffle Floodgate bridge In connection with the Spawning rebuilding of the sluice ground bridge in 1987, two fish Spawning ladders were built into the 1 ground metre high falls at the bridge such that fish now have free passage past the obstruction.

50 Completed watercourse rehabilitation projects

The northern of the two spillways was have restored free passage past the raised 10 cm. A large deep pool below obstruction for both fish and fauna. the spillway has been preserved by damming the river slightly where it The future merges with the new riffle behind the The project should be viewed in the island. context of the plan for the river Odense up to the year 2000 whereby Funen Impact studies in connection with County, in collaboration with the Munici- the restoration project palities and trade and industry, intends to Specific impact studies have not yet been develop the Odense river system into undertaken, but experience from similar European top-class trout waters. projects indicates that the new riffle will

Project data:

Project organizer: Funen County and Odense Municipality Contractor: Danish Land Development Service Project commenced: November 1993 The riffle viewed Project completed: June 1994 facing upstream Total costs: DKK 940,000 (excl. VAT) towards the island. Financing: Funen County, Danish Environmental Protection Agency and Odense Municipality

Watercourse data:

Catchment: 631 km2 The spawning Discharge: ground viewed Mean: 5,360 l s-1 facing downstream. Max: 36,470 l s-1 Min: 250 l s-1 Quality objective: B1 (Salmonid spawning and nursery waters) and/or B2 (Salmonid waters) Pollutional class: II and II–III (1993)

Restoration data:

Coordinates: 55° 24´ N10° 25´ E Length: 115 and 65 m Width: 18–24 m Slope: 5–12‰ Discharge capacity: 44,600 l s-1 Spawning gravel laid out: 390 m3 Stones laid out: 4,090 m3 Earth laid out: 4,160 m3 Earth excavated: 500 m3

51 .15 3.15 Funen County Lindved stream

Ann Fuglsang Annette Sode Claes Levin Pedersen at Hollufgård, Odense Watercourse system: River Odense Aim of the project the historical importance of the water mill In 1990, Odense Municipality planned to necessitated preserving the flow of water Introduction to the project establish a “prehistoric landscape” at the to the millpond. Culture Centre Hollufgård. Lindved stream is the In this connection, it was wanted to Implementation of the project lowermost county water- create a watercourse that on one hand In summer 1991, Odense Municipality and course that runs into the could form a natural part of a “prehistoric Funen County carried out the rehabilitation Odense river system. In landscape”, and on the other could project in collaboration with the National former times, the water- improve biological conditions in and Forest and Nature Agency. course had been channelized around the watercourse, including The new course of Lindved stream was upstream of the mill at restoring free passage past the obstruction approx. 2 km long (see sketch map). The Hollufgård (southeast of for the watercourse fauna. stream was led through the newly Odense), and was enclosed by Among other things, the plans established “prehistoric landscape” along dykes, partially obstructed, necessitated altering the course of Lindved part of the former path of the watercourse flat and slowly flowing. Over stream so that it ran through the land- Parkvandløbet. This reach of the water- the course of time, several scape along part of the former path of a course has a very flat cross-sectional valuable wet meadows had small watercourse called Parkvandløbet. profile and floods its banks in the winter. formed that were important Because of the valuable wet meadows Two ponds were excavated that serve as to preserve. From the along Lindved stream it was important to sand traps. A new course was excavated meadowland, Lindved stream preserve the high water level. Similarly, through the forest after which the stream ran through Hollufgård millpond and over a 2 metre high falls at the dam. This effectively obstructed the Culture passage of the stream fish centre Water and macroinvertebrates. mill Millpond tream Parkvandløbet ed s am dv am brook stre in stre gåen L gåen Ba Prehistoric Ba landscape Sketch map of the Møllebæk Forest N brook course of the stream before and Lindved after rehabilitation stream (scale approx Motorway 1:20,000). 52 Completed watercourse rehabilitation projects

The biological investigations encompass the following: Species composition and estimated coverage of aquatic and swamp plants (once yearly), species composition and relative number of aquatic macroinvertebrates (twice yearly), and species composition and number of fish inhabiting and passing through the reach (once yearly). Weed clearance has not hitherto been undertaken in the new reach. In order to investigate whether this will lead to drainage problems, the water level upstream of the reach is measured continually. The results of the investigations have not yet been reported, but some experience has already been gained.

Experience gained The number of species and number of plants and macroinvertebrates has increased steadily since rehabilitation of the stream. At the same time, physical conditions in the watercourse have changed considerably with the bed becoming increasingly varied as the banks have become more and more overgrown. Progress is least rapid at the shaded parts. The fish population increased steadily from 1991 to 1993 but was small in 1994. However, there are only very few if any fish in the most shallow, gentle and flat sections through the “prehistoric runs under a newly constructed aqueduct The riffle bypassing footpaths in the 20 hectare “prehistoric landscape”. that now leads Møllebæk brook along the mill dam landscape”. The area has subsequently Since completion of the project, Funen the former path of Lindved stream. From viewed facing been fenced in and highland cattle put County and Odense Municipality have set there the stream runs in part of the downstream out to graze. up a permanent exhibition on the former course of Bagåen stream to a towards the water interaction between watercourses and newly erected road bridge. From the road mill. Impact studies in connection with man. bridge to the water mill the new course the restoration project has been constructed as a stone riffle Following rehabilitation of Lindved stream The future thereby ensuring the fauna free passage regular biological investigations have The project should be viewed in the around the millpond dam. been undertaken in and around the context of the plan for the river Odense Discharge in Møllebæk brook is now stream, and the composition of the up to the year 2000 whereby Funen lower, but is still sufficient to preserve the streambed and depth of the water have County, in collaboration with the Munici- wet meadows and ensure adequate water been recorded. In addition, the water- palities and trade and industry, intends to flow to the millpond. course has been photographed regularly develop the Odense river system into Odense Municipality has established a from fixed positions. European top-class trout waters. highly ramified network of public 53 Completed watercourse rehabilitation projects

Project data:

Project organizer: Funen County and Odense Municipality Contractor: Danish Land Development Service Project commenced: May 1991 Project completed: July 1991 Total costs: DKK 1,180,000 (excl. VAT) Financing: Funen County, Odense Municipality, National Forest and Nature Agency

Watercourse data:

Catchment: 65 km2 Discharge: Mean: 420 l s-1 Max: 4,400 l s-1 Min: 26 l s-1 Quality objective: B1 (Salmonid spawning and nursery waters) Pollutional class: I – II and II (1993) The newly established course of Lindved Restoration data: stream through the “prehistoric land- Coordinates: 55° 24´ N10° 25´ E scape”. Length: 890 ® 1,820 m Width: 3–5 ® 2–6 m Slope: 0.4 ® 1–10‰ Meanders: 10 ® 24 Spawning gravel laid out: 180 m3 Stones laid out: 440 m3 Earth excavated: 6,800 m3

Technical aspects:

One concrete bridge One concrete municipal road bridge One concrete aqueduct Two lakes / sandtraps One wooden distribution structure Five wooden forest road bridges / footbridges Crossing a 30 cm dia. drain

54 3.16 .16 Funen County Holmehave brook

Ann Fuglsang Annette Sode Claes Levin Pedersen at Borreby Mill, Odense Watercourse system: River Odense

Introduction to the project Aim of the project an existing stone riffle up to the sluice. Holmehave brook is the next In 1988, the owner of Voldsgård, a farm The new course was constructed to have lowermost county water- through which the brook runs, approached an average slope of 1.1‰, and was course that runs into the river Funen County to enquire whether the excavated with a two-step profile. After Odense. In 1970, the water- County was interested in remeandering completion of excavation work, spawning course was channelized Holmehave brook upstream of Borreby grounds were laid out in the straight upstream of Borreby mill, mill. He was himself very interested, and stretches between meander bends, and immediately before it runs was therefore willing to give up the large stones were laid out to protect the into the river. As a result it necessary land free of charge. bends from the current. Since completion was canal-like, flat and slowly In connection with the County’s of the project, a public footpath has been flowing. At the same time as endeavours to improve conditions in established alongside part of the new the brook was channelized, watercourses, including free passage past watercourse. the millpond was dismantled, obstructions, it was agreed with the the sluice gate removed and owner to undertake a project aimed both Impact studies in connection with the inflow to the mill filled in at restoring free passage past the ob- the restoration project such that Holmehave brook struction at the sluice, and improving the Biological investigations have been ran through the remaining physical and chemical conditions in and undertaken both before and after the wing walls of the sluice. The around the watercourse. In view of the reach of Holmehave brook had been former brook bed upstream historical significance of the water mill, it remeandered. The biological investigations of the sluice was not filled in was important to preserve the remaining were undertaken once yearly during the completely, and in 1988 was wing walls of the sluice. period 1988–94, and encompassed the still visible in the terrain. At following: Species composition and the sluice, there was still an Implementation of the project estimated coverage of aquatic, swamp approx. 1.5 metre difference Before drawing up the project, the former and bank plants, species composition and in water level that effectively path of the watercourse upstream of the relative number of aquatic macro- obstructed the passage of sluice was determined from studying old invertebrates, species composition and fish and macroinvertebrates maps and probing the terrain. This path number of fish, as well as composition of in the watercourse. was roughly followed when excavating the bed sediment based on distribution the new watercourse. analysis of grain size. Free passage was created past the All the investigations were undertaken sluice by lowering the bottom of the at two locations in the new watercourse sluice approx. 1 metre and by extending reach as well as at two reference 55 Completed watercourse rehabilitation projects

locations located upstream of the remeandered reach. Weed clearance has not hitherto been undertaken in the reaches used for the investigations. The results of the investigations have not yet been reported in detail, but some of the experience can already be described.

Experience gained The number of plant species has increased since the brook was remeandered. With regard to macroinvertebrates, species composition can vary markedly at the locations investigated; as a consequence, changes in species composition have to be large before they can be ascribed to the restoration measure with any degree of certainty. Several unlawful toxic discharges upstream of the investigated reaches and inter-annual variation in bed conditions have thus caused large variation in macroinvertebrate species composition. However, conditions seem to have improved for the fauna in the lower part of the remeandered brook, although the change is not marked compared with the variation seen at the reference reaches. The trout population was very small immediately after the brook had been remeandered, and at several of the reaches investigated other fish species disappeared completely. In the following years, the trout population has grown in step with colonization by vegetation, and The riffle and modified sluice. the brook is now more varied, with weeds, pools and undercut banks. This N trend has been particularly marked since 1990, and the current fish population is Before restoration Borreby Mill generally considerably greater than before remeandering. As the new course has been Holmehave brook After restoration established in an area with a very loose soil structure, it was very unstable immediately after excavation. This unfortunate tendency was counteracted River Odense Å by laying out spawning gravel, but only really ceased when the banks and slopes Sketch map showing the course of Holmehave brook before and after restoration (scale approx. 1:5,500). became stabilized by vegetation.

56 Completed watercourse rehabilitation projects

The future The project should be viewed in the Project data: context of the plan for the river Odense up to the year 2000 whereby Funen Project organizer: Funen County County, in collaboration with the Munici- Contractor: Funen County palities and trade and industry, intends to Project commenced: September 1988 develop the Odense river system into Project completed: November 1988 European top-class trout waters. Total costs: DKK 270,000 (excl. VAT) Financing: Funen County and Danish Environmental Protection Agency

Watercourse data:

Catchment: 70 km2 Discharge: Mean: 640 l s-1 Max (20-year): 11,830 l s-1 Min: 35 l s-1 Quality objective: B1 (Salmonid spawning and nursery waters) Pollutional class: II and II–III (1993)

Restoration data:

Coordinates: 55° 22´ N10° 22´ E Length: 790 ® 910 m Width: 4.25 ® 3.75 m Slope: 0.3 ® 1.1‰ Meander bends: 2 ® 10 Spawning gravel laid out: 110 m3 Stones laid out: 75 m3 Earth excavated: 4,200 m3 Earth transported away: 1,000 m3

Technical aspects:

Four outfalls re-established Sluice and footbridge rebuilt Water mains crossed

57 . 17 3.17 Frederiksborg County Esrum stream

Birthe Petersen at lake Esrum Watercourse system: Esrum stream Aim of the project 2 km reach further downstream. Current In 1990, the County decided to restore concentrators were established along an Introduction to the project approx. 3.5 km of the stream, the aim approx. 500 metre reach by impaling being to create more varied physical stakes of split oak. The concentrators were Esrum stream starts at a conditions in the watercourse and hence established at 25 metre intervals alternately sluice in the northern part of improve its environmental quality. on the left and right banks of the stream. lake Esrum. The lake and Because of marked erosion, the bed of As a supplement to existing spawning much of its surroundings are one channelized reach was very wide. A grounds, spawning gravel was laid out under a preservation order. further aim of the project was therefore wherever bed conditions permitted. Moreover, a preservation to narrow the watercourse in that reach The majority of the practical work with order is under consideration and thereby attain a more varied bed. the project was undertaken by a firm of for Esrum Canal and the contractors selected from among four associated canals and historical Implementation of the project invited to submit tenders. In addition, monuments. The canal was The project was started in autumn 1990. spawning gravel and large stones were dug from lake Esrum to A 55 metre long spawning ground was laid out along an approx. 300 metre Dronningmølle at the begin- laid out near Esrum town and three other section at the beginning of the reach in ning of the 1800s. It enabled spawning grounds were laid out over a collaboration with local anglers. The wood to be transported from Gribskov forest to Copenhagen by barge. Esrum stream is one of the best fishing streams in Frederiksborg County. Sea trout migrate upstream and several reaches have a gravel bed and spawning grounds for trout. The stream was channelized at the end of the 1800s, but in most places now only appears slightly regulated.

Esrum stream. 58 Completed watercourse rehabilitation projects

County arranged for the gravel and stones to be transported to the site as Project data: well as for the hire of wheelbarrows, etc., while the anglers undertook the work of Project organizer: Frederiksborg County laying out the material. The contractor Contractor: Frederiksborg County completed the work in December 1990. Project commenced: October 1990 In 1991, a bypass was constructed Total costs: DKK 500,000 (excl. VAT) around the downstream millpond at Financing: Frederiksborg County DKK 325,000 (excl. VAT); Esrum Møllegård and there is now free Danish Environmental Protection Agency passage between the Sound and lake DKK 175,000 (excl. VAT) Esrum. Watercourse data: Impact studies in connection with the restoration project Catchment: 125 km2 The impact of the restoration project has Discharge: not been studied. Mean: 600 l s-1 Max: 1,400 l s-1 Experience gained Min: 300 l s-1 Planned initiation of the project was Quality objective: A (Areas of special scientific interest) and delayed as a result of complaints and B1 (Salmonid spawning and nursery waters) appeals by landowners during the formal Pollutional class: I–II (1993) processing of the case, and the field work was therefore undertaken at a time of Restoration data: year that was sub-optimal with respect to both the watercourse fauna and environ- Coordinates: 56° 00´ N12° 25´ E ment. Thus construction work was carried Length: 3,200 m out in the last three months of the year, Width: 2.5–3.5 m during which the sea trout migrate Slope: 3‰ upstream and when there are usually Discharge capacity: 1,800 l s-1 many rainy days that can delay the work. Meanders: 0 ® 8 The late time of the year also meant that Spawning gravel laid out: 150 m3 the vegetation that should have erased Stones laid out: 100 m3 the traces of theexcavation and spreading Earth excavated: 20 m3 of earth in and around the project area was slow to re-establish. Technical aspects: Despite the difficulties caused by the season the work schedule drawn up by Extension of three drains that formerly had their outfalls the contractor held. Access and work on spawning grounds roads for the excavators and transport of Establishing two manholes in connection with the above materials had to be reinforced by laying out metal plates and wood chippings, which increased the costs of the project. However, worries that the construction work would scare away the trout from the spawning grounds proved unfounded, and considerable spawning activity was seen at both the newly established and existing spawning grounds already while the work was being undertaken. 59 .18 3.18 Frederiksborg County Græse stream

Birthe Petersen at Frederikssund Watercourse system: Græse stream

Introduction to the project Aim of the project Implementation of the project Græse stream is a 15 km long The aim of the project was therefore to The study initiated in 1991 led in 1993 to watercourse that runs into restore free passage for fish at Græse Mill the establishment of a 125 metre long Roskilde Fjord. At Græse Mill by converting the falls to a riffle. In 1991, stone riffle upstream from the road approx. 3 km from the mouth Frederiksborg County therefore initiated a bridge, and a basin ladder downstream of the stream there was study of how this could be done. It was from the bridge. The stone riffle was previously a water mill. The already known that trout migrated up the established with a small winding current stream had been dammed lower part of the stream from Roskilde channel inthe watercourse profile in order there since construction of Fjord to Græse Mill, and a trout fry to ensure a reasonable water depth the mill. When the mill was stocking programme was undertaken during summer periods of low discharge. dismantled, there remained upstream of the falls. At the same time, the stream bed was an approx. 2.8 metre fall over an approx. 15 metre reach just after a road culvert. The water was held back by planks just before the culvert. The falls was only passable by eel via an eel pass. In the current County Plan, the designated quality objective for Græse stream is ciprinid waters. Because of improvement in the quality of the watercourse, consid- eration is now being given to raising the quality objective to salmonid spawning and nursery waters. Fulfilment of such a quality objective required that free passage for migratory fish be restored The basin ladder in at Græse Mill. Græse stream viewed facing upstream towards the road culvert. 60 Completed watercourse rehabilitation projects lowered such that the riffle fell evenly towards the road culvert. The planks in front of the road culvert were removed Project data: and a basin ladder constructed using 10 basins positioned such that there was a Project organizer: Frederiksborg County height difference of 31 cm between Contractor(s): Niels Lonnebjerg and Frederiksborg County adjacent basins. In order that the basin Project commenced: August 1993 ladder could blend into the surroundings Project completed: October 1993 as naturally as possible, the surfaces that Total costs: DKK 575,000 (excl. VAT) would be visible above the water level Financing: Danish Environmental Protection Agency were decorated with fist-sized pebbles. and Frederiksborg County The basin ladder was fitted with an eel pass. Watercourse data:

Impact studies in connection with Catchment: 28 km2 the restoration project Discharge: In connection with earlier trout stocking Mean: 75 l s-1 plans for Græse stream, experimental Max: 1,075 l s-1 release of trout fry was undertaken Min: 25 l s-1 upstream and downstream of the mill Quality objective: B3 (Ciprinid waters) dam. In its supervision programme for Pollutional class: II (1993) 1994–95, the County undertook studies aimed at determining whether sea trout Restoration data: can pass through the basin ladder, and whether the upstream migration of sea Coordinates: 55° 51´ N12° 05´ E trout results in successful spawning. Length: Riffles: 125 m Similarly, macroinvertebrate studies will Basin ladder: 30 m enable comparison of the restored reach Width, riffle: 1.25 ® 0.5–2 m with upstream reaches, and hence will Slope, riffle: 0.6 ® 6.1‰ reveal whether the improved physical Discharge capacity: conditions result in greater species diversity. Max: 1,000 l s-1 Min: 75 l s-1 Experience gained Gravel laid out: 210 m3 In order to prevent sediment transport Stones laid out: 210 m3 from the upstream reach to the riffle and Earth excavated: 150 m3 basin ladder during and following construction work, a sand trap was established upstream of the riffle. This proved to be a good idea as sediment transport from the upstream reach was greater than anticipated. Despite the establishment of the sand trap, which has been emptied several times since comple- tion of the work, it nevertheless proved necessary to empty the basin ladder of sand approximately half a year after completion of the work. The local inhabitants have shown great interest in the basin ladder, and often route their walks past it. 61 3.19 19. Copenhagen County Store Vejleå stream

Peter Malmolin Jørgen Johansen near Glostrup Watercourse system: Store Vejleå stream

Introduction to the project Aim of the project Remedial pumping of polluted ground- Store Vejleå stream runs in a Store Vejleå stream is one of the few water at the water supply borehole site 0.5–1 km wide river valley watercourses in the Copenhagen area ensures that there is always flow in the corridor that serves as a where the physical conditions are condu- stream as treated groundwater is pumped recreational green belt cive to attaining a high watercourse 2.7 km upstream through a high pressure -1 running through otherwise quality objective. As the watercourse also hose at the rate of 10–15 l s to be closely built-up districts on lies in an area of great recreational value, discharged again near the stream’s the outskirts of Copenhagen. it has been justifiable to invest the sum watershed. The stream is severely that the project costs. A number of large stones were laid channelized along its whole out in the watercourse profile to provide course. In one 1.5 km long Implementation of the project shelter from the current. In addition, reach the stream has been The construction work was undertaken stones and gravel were spread on the moved from former over the period 1992–94. The concrete stream bed. Three obstructions to the marshland and led through paving slabs were removed along a 1.7 passage of fish were removed and four two artificial lakes that serve km reach of the stream. The watercourse spawning grounds were laid out as stormwater basins with a was remeandered along its former bed storage capacity of approx. and a 400 metre stretch was rerouted Impact studies in connection with 0.5 million m3. completely. the restoration project The upper reach of Store The former paved section of the now Vejleå stream was regulated restored watercourse lacked any flora and in the 1940s and the sides fauna of significance. Since completion of and bed lined with concrete the restoration project, a monitoring paving slabs. This was done programme has been initiated to follow to protect the rather superfi- colonization by plants and animals. The cial water table at a nearby 30 cm thick clay membrane first data are being collected but no water supply borehole site conclusions can yet be drawn. from percolating diluted The watercourse profile was altered to The quality of the treated groundwater sewage. a two-step profile and lined with a 30 cm derived from remedial pumping at the thick clay membrane designed to hinder water supply borehole site is regularly hydraulic contact between the stream controlled relative to the criteria water and the superficial water table at stipulated in the discharge permit. the nearby water supply borehole site (see figure). The laying down of the clay The future membrane was one of the preconditions A large number of trout have been for undertaking the project. caught in the lower part of Store Vejleå 62 Completed watercourse rehabilitation projects

stream in recent years, many of which Store Vejleå stream were over 60 cm long. In the same reach, before and after Project data: a perch population is starting to form restoration. that on the basis of fish size measures up to the best Danish fish waters. At the Project organizer: Copenhagen County present time, there still remains to remove Contractor: Danish Land Development Service an obstruction to fish halfway up the Project commenced: 1992 watercourse system. When this has been Project completed: 1994 Water pumped Total costs: DKK 2,800,000 (excl. VAT) done, the fish population will be able to into stream spread upstream into the restored reach. Financing: Copenhagen County, Danish Environmental Protection Agency, N Experience gained Albertslund and Høje-Tåstrup Municipalities The project proved complicated to undertake because of the many different Watercourse data: interests at stake. On the other hand, Water supply 2 though, the project has attracted great borehole site Catchment: 9.8 km interest locally, and there has been good Discharge: -1 media coverage during the whole course Mean: 56 l s -1 of the restoration project. Angling Max: 930 l s Artificial Min: 15 l s-1 organizations have followed the project lakes with particular interest. Quality objective: B1 (Salmonid spawning and nursery waters) Pollutional class: “Cannot be determined” (1994)

Restoration data:

Coordinates: 55° 41´ N12° 25´ E Length: 1,547 ® 1,711 m Width: 1.5 ® 1.2/0.6 m (two-step profile) Slope: 2.7 ® 2.6‰ Discharge capacity: 930 ® 930 l s-1 Meanders: 0 ® 8 Spawning gravel laid out: 40 m3 Køge Bight Stones laid out: 550 m3 3 Outline map of Earth excavated: 5,700 m Store Vejleå stream. 63 3.20 Roskilde County 20. Køge stream

Anne-Marie Kristensen at Lellinge Watercourse system: Køge stream

Introduction to the project Aim of the project Implementation of the project Large sand deposits were regularly found Prior to establishing the sand trap, the Køge stream runs through in the reach that runs through meadow necessary authorization permits were largely agricultural land. The land and dredging was therefore necessary. obtained and compensation was agreed first 10 km have been re- The deposits had a detrimental impact on with the affected landowners. The practical stored through the construc- watercourse quality as sand migration work was undertaken by the County’s tion of current concentrators and frequent dredging reduced the own watercourse maintenance staff. and the laying out of gravel physical variation necessary to support a The sand trap was established outside and spawning grounds (see varied flora and fauna in the watercourse. the main course of the stream such that example 3.21). Thereafter, The designated watercourse quality part of the water ran through the main the watercourse runs objective for this reach of Køge stream is course, and part through the sand trap so through uncultivated salmonid waters. as to ensure the discharge capacity forested countryside and in In order to minimize the need to stipulated in the Provisional Order this reach the slope is suffi- dredge this reach of Køge stream and governing the watercourse. A 10 metre cient to prevent sand or thereby improve the physical conditions long culvert was established in the main sediment deposition. The to the benefit of fish, macroinvertebrates course dimensioned such that any lowermost part of Køge and plants, a sand trap was established in discharge in excess of 200 l s-1 would run stream runs through an area The sand trap on 1991 at the upstream end of the reach. through the sand trap, and that there of extensively farmed mead- Køge stream ows before flowing out into Køge Bight. Along this reach, the stream is a meandering watercourse with a good environmental quality.

64 Completed watercourse rehabilitation projects was free passage to fauna throughout the year. Project data:

Impact studies in connection with Project organizer: Roskilde County the restoration project Contractor: Danish Land Development Service Biological investigations have not been Project commenced: June 1991 undertaken in the project area or down- Project completed: September 1991 stream of the sand trap especially aimed Total costs: DKK 266,350 (excl. VAT) at revealing the effects of the project. Financing: Roskilde County and The pollutional class of the stream Carlsen-Langes Foundation upstream and downstream of the sand trap has remained unchanged at an Watercourse data: unsatisfactory level. One of the greatest problems with Køge stream with respect Catchment: 153 km2 to fulfilling the watercourse quality Discharge: objective is the very low discharge in Mean: 900 l s-1 summer, which makes it difficult to achieve Max (10-year): 11,500 l s-1 a more satisfactory pollutional class. Min: 10 l s-1 Quality objective: B2 (Salmonid waters) Experience gained Pollutional class: II–III (1990–94) The project was undertaken in 1991 and sand has since been removed from part Restoration data: of the sand trap once in summer 1992 and from the whole sand trap once in Coordinates: 55° 28´ N12° 08´ E 1994. The sand trap has functioned as Length: 200 m expected and the excavated sand has Width: 5 m been used to raise the ground level of the Slope: 0.6‰ area around the lake/sand trap. Discharge capacity: 8,000 l s-1 The area has rapidly become overgrown with vegetation, and trees and bushes have been planted out. The whole area now appears as meadow land of natural beauty, especially in winter, when the water level in the lake/sand trap is high.

65 3.21 Roskilde County 21. Køge stream

Anne-Marie Kristensen at Bjæverskov Watercourse system: Køge stream

Introduction to the project Aim of the project prised three types of restoration measures Køge stream was formerly a The aim of restoring this reach of Køge as well as the establishment of spawning pearl among the water- stream was to create varied physical grounds and planting of vegetation courses of Zealand, having a conditions in the watercourse so as to alongside the stream. Type 1 comprised very rich and varied fish fulfil its quality objective as salmonid the laying out of stone heaps as well as community. Thus around the spawning and nursery waters. The individual large stones, and was under- beginning of the century, it physical measures taken were thus taken in reaches where restoration was was possible to catch numerous designed to enhance the environmental not allowed to reduce the drainage sea trout in the lower reaches quality of the watercourse as well as to capacity. Type 2 comprised laying out of the stream. minimize the need for maintenance of stone heaps and gravel riffles, and was At Bjæverskov, the stream the reach. undertaken inreaches with a slope runs through an area with exceeding 2‰. Type 3 comprised the intensive agriculture and was Implementation of the project laying out of gravel beds and individual characterized by former The restoration work was undertaken in large stones, as well as large stone heaps channelization and rather the period 1990–92. The project com- as current concentrators, and was hard-handed maintenance. Much of the reach had deepened to more than half a meter below the stream bed stipulated in the Provisional Order governing the stream. Moreover, it was canal-like with little physical variation and little possibility for a varied flora and fauna.

Laying out stones and spawning gravel in Køge stream. 66 Completed watercourse rehabilitation projects undertaken in reaches where former maintenance and erosion had made the Project data: watercourse too deep or too wide, and where small falls had formed at drain Project organizer: Roskilde County outlets. Contractor: Danish Land Development Service With all three types of restoration, Project commenced: October 1990 spawning grounds were established if Project completed: November 1992 conditions were otherwise suitable. At a Total costs: DKK 924,830 (excl. VAT) few reaches, restoration actually reduced Financing: Roskilde County and the discharge capacity of the water- Danish Environmental Protection Agency course, but in no case did it fall below that stipulated in the Provisional Order Watercourse data: governing the watercourse. Catchment: 130 km2 Impact studies in connection with Discharge: the restoration project Mean: 350–800 l s-1 At two experimental reaches, the fish Max: 3,300–10,000 l s-1 population was investigated by electro- Min: 0–6 l s-1 fishery before and after restoration. At Quality objective: B1 (Salmonid spawning and nursery waters) one of the reaches, the number of species (not fulfilled) increased from 2 to 6, thus indicating real Pollutional class: II–III (1991–94) progress. At the other reach, there was no evident corresponding effect, however. Restoration data: The density of trout in the two reaches is still very low. At the reach with the Coordinates: 55° 28´ N12° 02´ E least slope, trout have not been detected Length: 9,260 ® 9,260 m since 1992, while at the other reach, Width: 2.25–5 ® 2.25–5 m trout density is tending to increase Slope: 0.55–5.7 ® 0.55–7‰ slightly. Discharge capacity: ~ 6,000 l s-1 Macroinvertebrate samples were also Spawning gravel laid out: 400 m3 collected at the two reaches before and Other gravel laid out: 3,000 m3 after restoration. The number of clean- Stones laid out: 1,500 m3 water macroinvertebrates in the stream Earth excavated: 90 m3 seems to be on the increase since their number has increased in both experimental reaches.

Experience gained content of the stream water and the Despite the improved physical conditions relatively low water level and slow current in the restored reach the fish and macro- promote the occurrence of massive invertebrate studies have not revealed any growths of filamentous algae. The result clear improvement in the environmental is marked daily fluctuation in the oxygen quality of Køge stream. content of the water. A probable explanation is the great Another reason for the slow colonization variation in discharge in the stream, by clean-water macroinvertebrates is which is very low in summer, thereby probably that there are no reaches precluding a satisfactory pollutional class. immediately upstream of the restored During the summer, waste water reach that house such species. discharged to the stream is only diluted very slightly, and the high nutrient 67 . 22 3.22 Storstrøm County River Suså at

Poul Debois Holløse Mill, Skelby Watercourse system: River Suså

Introduction to the project The Suså river system drains an Aim of the project Implementation of the project approx. 815 km2 catchment In 1991, the main channel sluice gate The project was undertaken in winter area and is the largest river broke down and the other sluices proved 1992–93. The remainder of the main system on Zealand. At Holløse to be in a state of disrepair. As the fish channel sluice gate with the eel trap was Mill, the catchment area is ladder is unlikely to ever have been removed and replaced by a new, larger 753 km2. The river is charac- sufficient to ensure adequate passage for sluice gate. The fish ladder was preserved terized by marked seasonal fish, this gave rise to the total renovation and shall primarily serve as a drop sluice variation in discharge. Summer of the whole area. for migratory fish. In connection with the discharge at Holløse Mill can The aim of the project was therefore project, approx. 1 km of dykes was thus be as low as a few to ensure flow and water level regulation renovated along the main channel. hundred litres per second, in the river Suså and the lakes Tystrup and The sluice gate in the secondary while the highest discharge Bavelse, to preserve the historical value of channel, “The Daneskjoldske canal“, was measured there was 37,000 l s-1. the area and to create a functional fish dismantled and replaced by a riffle. The At Holløse Mill, among and fauna passage by establishing a riffle. latter was sited in a manner that best structures of historical In 1991, a similar riffle was built at the preserved and protected the structures of interest, the river Suså divides river Suså’s outlet to the sea. The river has historical interest. Since a false guide into two channels that merge probably been effectively closed to the current can form at the main channel again downstream of the passage of migratory fish since the 13th sluice gate during periods of high winter mill. The two channels were to 14th centuries. Establishment of the discharge, a current concentrator was each regulated by a sluice two riffles should therefore open up the constructed to guide the fish to the riffle. gate, thereby also regulating whole Suså river system to migratory fish. In addition, a new bridge was built over the water level in two lakes the canal to replace the road that once further upstream. Flow was led over the dismantled sluice gate. further regulated by an Riffle Impact studies in connection with additional spillway/sluice Daneskjoldske gate near the main channel canal the restoration project Electrofishery undertaken at the riffle in sluice gate, as well as by the Fish ladder and Bypass autumn 1994 revealed the presence of intake to a turbine. The main new sluice gate reach channel sluice gate, which Turbine gudgeon, burbot, spiny-finned loach, eel incorporated an eel trap, was and roach. Holløse Mill had previously fitted with a fish ladder obstructed passage to the whole of the incorporating an eel pass in Sketch map of the upstream river system. Future electro- 1987. vicinity at Holløse fishery will reveal the riffle’s value as a Mill. passage for migratory fish. 68 Completed watercourse rehabilitation projects

Project data:

Project organizer: Storstrøm County Contractor(s): Waterconsult (outline) and Danish Land Development Service Project commenced: November 1992 Project completed: March 1993 Total costs: DKK 2,000,000 (incl. VAT) Financing: Storstrøm County, Vestsjælland County and Danish Environmental Protection Agency

Watercourse data:

Catchment: 753 km2 Discharge: Mean: 2,941 l s-1 Max (median): 21,900 l s-1 Min (median): 600 l s-1 Quality objective: Upstream: A (Areas of special scientific interest) / B3 (Ciprinid waters) Downstream: A (Areas of special scientific interest) / B2 (Salmonid spawning and nursery waters) Pollutional class: II (1993)

Restoration data:

Coordinates: 55° 19´ N11° 42´ E Length: 140 ® 140 m Width: 9 ® 2–9 m (two-step profile) Slope: Fall 14.5‰ Discharge capacity: 5,200 l s-1 Meanders: 4 Stones laid out: 1,000 m3 Experience gained The sluice gate at Earth excavated: 1,200 m3 The project has always worked as ex- Holløse Mill (upper) pected, there always being water flow in and the riffle at Technical aspects: the riffle with water only flowing over the Daneskjoldske canal main channel sluice gate during periods (lower). Dismantling of two sluice gates and eel traps of high discharge. Construction of new sluice gate incorporating fish ladder and eel pass It is too early to draw conclusions Construction of riffle passable by fish about the possibilities for fish to pass the Construction of bridge riffle as sufficient electrofishery has not yet Renovation of 1 km dikes been undertaken upstream of Holløse Mill. Establishment of current concentrator The project was undertaken in successful close cooperation with the local museum, which has had the opportunity to investigate the structures associated with the Daneskjoldske canal. 69 .23 3.23 Storstrøm County Lilleå stream

Poul Debois at Kongsted Watercourse system: Fakse stream Aim of the project Implementation of the project The aim of the project was to restore an The project was undertaken in winter Introduction to the project open watercourse with sufficient discharge 1993–94. A 600 metre length of the capacity and good physical conditions culvert was removed and re-established as Lilleå stream is a tributary of sufficient to fulfil the watercourse quality an open watercourse. It was not possible Fakse stream, and is a clean- objective, as well as to recreate the to open the remaining 100 metres of the water watercourse with a stream as a part of the stream valley. culvert as a single landowner did not wish good slope and relatively to participate. The banks were reinforced good physical conditions. The with stones and stones were laid out on designated watercourse the stream bed at short intervals in order quality objective for the Park to create a meandering course that in stream is salmonid spawning effect serves as a two-step cross-sectional and nursery waters. The Culverted profile. Three minor track crossings were quality objective for the upper reach established and a larger diameter culvert reaches running through was fitted under an existing track. In previously intensively culti- addition, a sand trap was established in vated land was not fulfilled the downstream part of the reach, and because a 700 metre reach of Sand trap groups of local deciduous trees were the stream was culverted. In planted along the reopened stream. addition, there was a mill- Attempts were made to render the pond and associated dam. remaining 100 metre culverted section passable by establishing an inflow manhole upstream of the culvert. The Reopened reach manhole is fitted with a plate at water level height that prevents branches etc. Bridge from entering the culvert.

Impact studies in connection with the restoration project No impact studies have yet been under- taken but the project will be followed up N by fauna studies and electrofishery. The studies will show whether the remaining Sketch map of the culvert still comprises a hindrance to the 100 m reopened reach of passage of fish. Lilleå stream. 70 Completed watercourse rehabilitation projects

Experience gained establish the whole of the culvert as an As restoration projects are generally open watercourse. Despite this the undertaken on a voluntary basis, it is project was still undertaken, it being often difficult to achieve the optimal judged that opening the remaining 600 result. A weakness of the present project metres would in any case enhance the is thus that it has not been possible to re- value of the landscape and environment.

Project data:

Project organizer: Storstrøm County Contractor: Danish Land Development Service Project commenced: November 1993 Project completed: December 1993 Total costs: DKK 400,000 (excl. VAT) Financing: Storstrøm County

Watercourse data:

Catchment: 2.6 km2 Discharge: Mean (summer): 5 l s-1 Mean (winter): 30 l s-1 Max: 79 l s-1 Min: 0.1 l s-1 Quality objective: B1 (Salmonid spawning and nursery waters) Pollutional class: Not assessed because culverted

Restoration data:

Coordinates: 55° 15´ N12° 03´ E Length: 700 ® 700 m Width: 1 m (pipe) ® 1 m Slope: 6‰ Stones laid out: 80 m3 Earth excavated: 3,000 m3

Technical aspects:

Removal of 600 metre long culvert Widening a culvert under a track Crossing electricity cables Establishing three track crossings

The new stream in summer 1994 (upper) and in winter 1995 (lower).

71 3.24 Bornholm 24. County Søbæk brook at Neksø

Klavs Nielsen

Watercourse system: Aim of the project Søbæk brook It the 1980s, it was observed that there was a sea trout population in the brook Introduction to the project with several spawning grounds. However, Søbæk brook arises approx. 6 the latter were threatened by sand km southwest of Neksø. The migration, and the possibilities for catchment area is a low-lying maintaining the population were there- agricultural area. Nearly the fore limited. The aim of the project was whole of the watercourse is to improve conditions for plants and channelized, which is unusual animals in and around the watercourse by Restoration of Søbæk brook. on Bornholm. The slope relaying the main channel along an averages 3.2‰, and is greatest approx. 350 metre reach and establishing Implementation of the project at the source. The lower half a couple of small lakes. The local angling association entered into of the brook runs through an agreement with a local landowner and raised seafloor that has thereafter approached the County. The previously been meadow and Watercourse data: project was carried out in autumn 1991 marshland. using state funds for nature restoration Catchment: 13 km2 projects. In connection with the relaying Quality objective: B4 (Watercourses with the main channel a couple of small lakes varied flora and fauna were established in the area and a short but of little value to fish) reach of a minor tributary was restored. Pollutional class: II (1985) In addition, a sand trap was established in the new watercourse to prevent Restoration data: sanding up of downstream spawning grounds. The former channelized water- Coordinates: 55° 04´ N15° 08´ E course was preserved so as not to have to Length: 334 ® 381 m move drains and tributaries. Width: 1.5 ® 2–3 m After an unstable period with sand Slope: 0.5‰ migration, a riffle was established Meanders: 0 ® 5 uppermost in the restored reach. This has Stones laid out: Scattered subsequently been used as a spawning ground. Technical aspects: Experience gained Two new crossings established The project attracted considerable public attention, and the landowner has been awarded an environmental prize by the Bornholm Angling Association. 72 4 Hans Ole Hansen Brian Kronvang Bent Lauge Madsen Classification system for watercourse rehabilitation

Proposal for a classification system only concerns rehabilitation system projects that benefit the environment, though, and rehabilitation projects solely Denmark is currently well to the forefront undertaken to improve drainage are not in the watercourse area, both with included. respect to legislation, administration, Even though considerable efforts have rehabilitation, and protection. Unfortu- been made to design the classification nately, though, no clear statistics have system as unambiguously as possible, it is been compiled of Danish restoration inevitable that there will be some projects, and no clear overview is avail- obscurities and overlap. It is nevertheless able of the number and type of projects hoped that the proposed system can form undertaken in Denmark. the basis for a database on the rehabilita- In order to obtain a useful overview of tion projects previously or currently being the projects undertaken and in order to undertaken in Denmark. In addition, it is be better able to steer future rehabilitation hoped that further development of the projects in the right direction, it is proposed classification system will lead important to compile statistics on the other European countries to establish projects and undertake continuous similar databases. systematic collection of information. The various national databases could A precondition for being able to compile subsequently be compiled and updated such statistics, however, is the availability under the auspices of the European of an unambiguous classification system Centre for River Restoration. The informa- for the different types of restoration tion compiled could eventually be made project and methods. Without clear available on the Internet and GIS definitions, one cannot expect that the (Geographical Information System). This questions and answers will be interpreted will give interested parties the possibility in the same way from person to person. to study the database and retrieve specific In the present chapter, we therefore information for their own use directly to put forward a proposal for a classification their own computers. In addition, it system for watercourse rehabilitation would eventually enable registration of projects (Appendix A). The classification projects to be decentralized. 73 Classification system for watercourse rehabilitation

Proposed classification system Type 1 The classification differentiates between Type 1: Rehabilitation of watercourse reaches “Type” and “Method”. The rehabilita- Reach remeandered tion projects are subdivided in three types Culverted reach opened to create better habitats according to the overall objectives of the Two-step cross-sectional profile created project. Subdivision of rehabilitation Type 2 Lakes established/re-established in connection with the watercourse projects by type is based on the extent of Ochre sedimentation basin established in connection with the watercourse rehabilitation within the watercourse Stones laid out system, as shown schematically in Figure Gravel laid out 4.1. Each type encompasses the methods Type 3 Artificial fish hiding places established that can be used to achieve the objective. Other solid objects laid out Rehabilitation project types and methods Current concentrators established are summarized in Table 4.1. The list is Sand traps constructed open, though, and may be expanded. Trees and bushes planted within the 2 metre cultivation-free border zone Trees and bushes removed within the 2 metre cultivation-free border zone Type 1: Rehabilitation of watercourse Figure 4.1. Artificial bed and/or bank established (fascines, concrete, paving slabs, etc.) reaches, encompasses projects whose Schematic defini- Artificial bed and/or bank removed (fascines, concrete, paving slabs, etc.) objective is local improvement of shorter tion of the three Other methods: fences, watering places, etc. reaches. The methods used under type 1 types of rehabilita- Other will typically result in better habitats tion project. locally, both in the watercourse and in the 2 metre cultivation-free border zone. Type 2: Restoration of continuity between watercourse reaches Obstruction replaced by riffle Type 2: Restoration of continuity Obstruction replaced by meanders between watercourse reaches, encom- Bypass riffle established at preserved obstruction passes projects aimed at ensuring free Riffle established at preserved obstruction passage along watercourse systems. The Culverted reach opened to create free passage methods employed under type 2 are Culvert falls evened out (drop manhole removed, etc.) those that reconnect reaches and restore Greater water depth and/or current breakers in underpass culverts free passage and continuity between a Falls evened out at culvert outlet/bridge watercourse’s component reaches and Fish ladder/fish sluice established/removed between the watercourse and its immedi- Formerly periodically “dried-up” stream reach completely restored ate surroundings. Formerly periodically “dried-up” stream reach partly restored Water pumped into stream to maintain flow in periodically “dried-up” reach Type 3: Rehabilitation of river valleys, Otter pass established encompasses projects affecting both the Other watercourse and its whole river valley. The methods employed under type 3 are Type 3: Rehabilitation of river valleys those that ensure that the watercourse and river valley function as an ecological Water table and flooding frequency increased by and hydrological entity. Their impact – remeandering the watercourse reaches across the watercourse and its – raising the bed surroundings. – terminating drains in meadows – establishing a dam With this basic classification system as a – meadow trickling foundation, the next phase is to develop – narrowing the watercourse a system that can be employed in Table 4.1. Water- Lakes/ponds/wetlands etc. re-established/established in the river valley questionnaires and databases. There has course rehabilita- Vegetation management in the river valley to be room for rehabilitation types and tion – types and Other methods to be combined, though, in as methods. 74 Classification system for watercourse rehabilitation unambiguous a manner as possible. Our proposal for a coming questionnaire is given in Appendix A.

Examples of methods The methods encompassed by each type are those used to achieve the objective of Figure 4.2. Remeandering of watercourse that restoration project type. Examples of reaches can serve several purposes, and is the individual methods are illustrated in therefore included under all three rehabili- Figures 4.2 to 4.19. tation project types. Under type 1, remeandering creates more varied habitats Type 1 encompasses methods used for in the watercourse, among other things making local improvements in water- because of the resultant alternation course reaches and the 2 metre cultiva- between deep and shallow parts and weak tion-free border zones along their banks and strong current. In addition, the current so as to provide better habitats for in meandering watercourses hinders animals and plants (Figures 4.2 to 4.9). sanding over of the gravel and stones.

Figure 4.3. A two- Figure 4.4. Stones provide hiding places for step cross-sectional fish and habitats for stream macroinverte- profile ensures an brates. They also improve habitat condi- adequate water tions by causing currents such that the depth and current water becomes oxygenated. in dry periods.

Figure 4.5. Gravel banks serve as spawning grounds for fish and as a habitat for stream macroinvertebrates. 75 Classification system for watercourse rehabilitation

Figure 4.6. Setting up artificial hiding places for fish was one of the original rehabilitation methods allowed under the Danish Watercourse Act, but is seldom used nowadays. Figure 4.8. Sand traps reduce the transport of sand in watercourses.

Figure 4.7. Current concentrators – made, for example, by placing Figure 4.9. Trees and bushes planted within the 2 metre cultivation-free border zone can mounds of coarse gravel on alternate sides of the watercourse – stabilize the banks and create hiding places for fish. In other places, it can be an advan- ensure that the current is strong enough to keep the gravel banks tage to remove trees and bushes. free of sand.

76 Classification system for watercourse rehabilitation

Type 2 encompasses the methods that restore free passage between watercourse reaches, thereby enabling the fauna to move freely between the different parts ofthe watercourse and between the watercourse and its immediate surround- ings (Figures 4.10 to 4.16).

Figure 4.10. Obstruction replaced by a riffle. Figure 4.12. Culverted reach opened. If the primary objective is to restore free passage between two reaches, the method comes under type 2. However, if the primary objective is to create better habitats in the formerly culverted reach, then the project is classified as a type 1 project – even if it also restores free passage between two Figure 4.11. Bypass riffle established at reaches. Thus one must always bear in preserved obstruction. In cases where one mind the primary objective. If one is in wants to preserve an obstruction, e.g. a doubt, one has to make a decision. hydroelectric power station or a historical water mill, but at the same time ensure free passage to the fauna, a solution can be a bypass riffle.

Figure 4.13. Current breakers in underpass culverts. In order to enable fish to pass through a culvert one can raise the stream water level and insert current breakers.

77 Classification system for watercourse rehabilitation

Figure 4.14. Falls evened out at culvert outlet. In cases where the outlet of a culvert, e.g. at a road underpass, is higher than the stream water level (left), one can establish a short riffle or lower the culvert to the level of the stream (right). Figure 4.15. Fish ladders were one of the first Danish rehabilitation measures undertaken, but are now only used in cases of need, for example if there is insufficient Figure 4.16. Otter pass. This is a type 2 space to establish a bypass reach. A rehabilitation method that helps otters to watercourse reach can also be improved by pass under bridges. Many otters are killed removing a fish ladder and replacing it by vehicles in Denmark when trying to cross with a riffle or a bypass reach. roads over streams.

78 Classification system for watercourse rehabilitation

Type 3 encompasses methods aimed at improving contact between the water- course and its river valley through raising the water table in the meadows and ensuring that the watercourse can flood over into the meadows when the water level is high. A higher water table and more frequent flooding can be desirable, for example if one wants to reduce sediment transport or the stream water nitrogen or ochre content. The methods are generally the opposite of those used to drain the meadows in the past (Figures 4.17 to 4.19).

Figure 4.17. Water table and flooding frequency increased by raising the bed. One can also raise the water table and increase the frequency of flooding by raising the watercourse bed, for example by establishing high riffles (shown here during a dry summer). Figure 4.18. Water table and flooding frequency increased by remeandering the watercourse. One can raise the water table and increase the frequency of flooding by remeandering the watercourse.

Figure 4.19. Lakes, ponds and wetlands can be established or re-established in the river valley, for example by excavation or by damming the watercourse. 79 5 Hans Ole Hansen Brian Kronvang Bent Lauge Madsen Environmental impact of watercourse rehabilitation

In order to be able to assess whether the To date, only few actual impact objective of a watercourse rehabilitation assessment studies have been undertaken project has been attained, one has to as follow-ups to rehabilitation projects in investigate the project’s impact on the Denmark. Some of these have been watercourse and its immediate surround- carried out as part of already existing ings. The impact studies have to be watercourse pollution monitoring designed according to both the project programmes, while others have been type and the objective. If the main planned and carried out as direct follow- objective of the rehabilitation project is to ups of the rehabilitation projects. remove an obstruction between two While the biological impact of rehabili- watercourse reaches to restore free tation of watercourse reaches often first passage for fish and stream macroinverte- becomes apparent after some time, the brates, one has to focus on investigating physical effects are normally easily the impact of restoration on the upstream demonstrable, for example in the form of populations of migratory fish (e.g. trout) a removed obstruction, new spawning and macroinvertebrates. If the main grounds or a new meandering course objective of the project is to restore the with all its natural characteristics such as riparian areas to their original condition, meander bends, riffles and periodically then one has to focus more generally on flooded riparian areas. the impact on plants, animals and birds, This section presents a small selection as well as on retention and/or turnover of of each of the three main types of water- water, nutrients and organic matter in the course rehabilitation project described in riparian areas. Chapter 4. Although the selection focuses In connection with watercourse on the positive effects that rehabilitation rehabilitation, one has also to bear in can have on watercourse quality, the mind that aesthetic considerations and impact studies should naturally also user interests are nearly always involved. encompass possible negative effects. Impact studies can therefore also involve Moreover, it is essential that one pays user opinions as to the watercourse’s close attention to assessment criteria. For appearance and utility value after rehabi- example, flooding can be assessed as litation. positive from the viewpoint of water 80 Environmental impact of watercourse rehabilitation quality, but negative from the viewpoint of cultivation of the flooded fields. In the Before remeandering After remeandering following, the impact of rehabilitation is mainly examined from the viewpoint of Watercourse length 1,340 m 1,850 m its impact on nature and the environment. Discharge capacity 6.6 m3 s-1 3.5 m3 s-1 No. of meander bends 0 16 No. of spawning grounds Few 18 (3,500 m2) Type 1: Rehabilitation of Periodically wet riparian areas 0 approx. 2,000 m2 watercourse reaches

Form and shape Table 5.1. Physical conditions at Gelså stream before and after pools and riffles. The current will be slow The physical changes that have been remeandering in 1989 (1). in the shallow areas that form near the made to Danish watercourses have had banks on the outer side of the meander many negative effects on watercourse 40 bends, but rapid on the inner side of the quality. Channelization, deepening and A B meander bends and at the shallow riffles 1988 1988 the lack of cultivation-free border zones 30 that form between them. Such physical alongside the watercourses have en- variation is a characteristic of naturally hanced sediment input and led to the loss meandering lowland watercourses. Thus 20 of the natural stone and gravel bed. This instead of a watercourse with a roughly impoverishment of physical conditions uniform depth and width, remeandering has resulted in the loss of habitats, 10 gives one with great physical variation. thereby critically affecting the survival of 1991 Among other places in Denmark, this has Frequency distribution (%) 1991 many plant and animal species. The path 0 been documented for Gelså stream (1) to recreation of the lost habitats in our 7 8 9 10 11 12 13 1.0 1.2 1.4 1.6 1.8 2.0 (Figure 5.1 and Table 5.1). The project Watercourse width (m) Maximum depth (m) watercourses is rehabilitation and a recreated a longer course, several switch to more environmentally sound Figure 5.1. Variation in the width (A) and maximum depth (B) of meanders, riffles and spawning grounds, maintenance practices. Gelså stream before (1988) and after (1991) remeandering. Stream and increased the ecologically important The amount of sediment input to our width varied from 9–12 metres in 1988, and from 7–14 metres in area of the riparian zone subject to channelized watercourses in many cases 1991. Stream maximum depth varied from 1.4–1.9 metres in 1988, periodical flooding. exceeds the watercourse’s capacity to and from 1–2 metres in 1991. Thus on average, the watercourse Existing experience with the monitoring transport the sediment away. This raises has become narrower and more shallow after remeandering, of watercourse remeandering projects in the watercourse bed, resulting in a uniform thereby increasing the possibility of flooding. Denmark indicates that considerable bed of migratory sand. In contrast, erosion takes place in the watercourse naturally meandering watercourses with during the actual construction phase, as dimensions appropriate to the volume of 40 well as during a subsequent period of A: Winter 1989-90 B: Winter 1990-91 water draining from the catchment area adjustment (Figure 5.2). However, much are in dynamic equilibrium with respect to 30 of the transported sand can be caught sediment input and transport. In addition, using a temporary sand trap established the watercourse will be much better able 20 immediately downstream of the remean- to adapt to a change in sediment input dered reach. In contrast, though, the fine since both the pools and the periodically particulate matter will more easily escape 10 flooded riparian areas function as buffers from the reach, thereby augmenting in the form of sedimentation areas. sediment transport in the water for a Frequency distribution (%) Rehabilitation in the form of remean- 0 shorter or longer period. Experience with dering of watercourse reaches and -2 -1 0 1 -2 -1 0 1 2 the remeandering of Gelså stream has Erosion (m3)Deposition (m3) Erosion (m3)Deposition (m3) introduction of environmentally sound thus shown that following a period of watercourse maintenance helps to Figure 5.2. Erosion and deposition of bed material in Gelså stream considerable erosion during the first recreate natural variation in watercourse during the first (A) and second (B) winter after remeandering. The winter, the watercourse entered a phase form and shape. It endows the watercourse figure is based on precision surveyance of 120 cross-sectional of net deposition, primarily near the banks with varied current conditions and creates profiles. and on the flooded riparian areas. Thus 81 Environmental impact of watercourse rehabilitation two years after remeandering, dynamic Figure 5.3. Diagram problem as a current exceeding 80 cm s-1 Tubing for colection equilibrium had not been reached (1). of the net cage can wash the eggs out of the spawning of porewater placed in the ground. Spawning possibilities for trout spawning ground. On the basis of these impact studies, it Establishment of new spawning grounds Pore water samples can be concluded that for spawning for trout is one of the most common are collected at a Spawning ground grounds to be able to function, transport forms of rehabilitation in Danish water- depth of 10 and 20 of fine material has to be low. Thus in courses. The grounds are often established cm using porewater sediment-plagued watercourses, one has simply by laying out gravel mixed with sampling probes to take measures to deal with the source stones at regular intervals along water- connected to the of the problem, as well as measures to courses. surface by tubing. reduce sediment transport. Examples In order to investigate the utility of include establishing paved watering new spawning grounds, it is not sufficient places in parts of the watercourse where just to investigate whether trout spawn in cattle trample down the banks, enforcing Pore water them or whether they contain eggs in the sampler regulations concerning the Danish 2 metre spawning season. One has also to cultivation-free border zone along investigate how many fry hatch from the watercourses, and switching to a weed Net cage filled with gravel the following year. In many cases, spawning gravel clearance practice that protects the banks the majority of the eggs die before against erosion by the current. One can hatching because the gaps between the eggs died of oxygen deficiency. It is also reduce sediment transport over gravel particles silt up with sand, mud or therefore insufficient just to ensure a spawning grounds by establishing a sand ochre. Silting-up of spawning grounds good current over the spawning ground trap. Sivebæk and Bangsgaard (4) have can present a major problem in Danish since this will only keep the surface clean shown that trout eggs survive best in watercourses. An example of this was – material can still be forced down into spawning grounds protected by a sand seen in an experimental project in 1987, the gaps in the gravel. Thus the transport trap located immediately upstream. where spawning grounds were established of sand and other fine material over the in ten watercourses (2). Electrofishery the spawning grounds has to be sufficiently Habitats for trout fry following spring revealed the presence of low if spawning is to be successful. Spawning grounds are not the only trout at only four of the spawning grounds, Sivebæk and Bangsgaard (4) modified precondition for maintaining a satisfactory and after the first winter period, the the “egg cage” by fitting it with two trout population. Suitable habitats have majority of the new spawning grounds probes for the collection of porewater for also to be available for the fry that hatch contained 5–20% more fine material the measurement of the oxygen concen- from the gravel. Mortality at this stage is (<2 mm) than when they were laid out Figure 5.4. At first, tration in the spawning gravel (Figure 5.3). very great. Numerous studies from Denmark the preceding autumn. the trout fry keep They too found that the eggs died when and abroad show that the number of Larsen and Henriksen (3) have to the shallow the amount of fine particles exceeded a hiding places (in particular weed) and an developed a method able to assess the water and weeds certain low level. Moreover, they found appropriate low water depth and current condition of the eggs and the early stages close to the bank (5). that a strong current did not help with the are decisive determinants of the survival of trout in spawning grounds. The eggs rate of the young trout (5). The best way are placed in a net cage filled with gravel 50 June August to ensure good conditions for newly which is then buried in the spawning hatched fry is therefore to ensure that the ground. Aftersome weeks or months, the 40 watercourse fulfils these conditions cages are retrieved. Before retrieval, (Figure 5.4). 30 though, the cages are enclosed in a The final proof of successful spawning plastic “sock” to prevent material from is the development of a satisfactory 20 being washed out. Experiments population of salmonids in those water- undertaken with the cages in watercourses courses where stocking is not undertaken. Percentage of trout 10 revealed that the presence of very small In Ribe County, the watercourse quality amounts of fine material was sufficient to 0 objective salmonid spawning and nursery block the gaps between the gravel 1 50 100 150 200 250 300 350 4001 50 100 150 200 250 300 350 400 waters is being fulfilled by an increasing particles so much that a large part of the Distance to bank (cm) number of watercourses (Figure 5.5) (6). 82 Environmental impact of watercourse rehabilitation

1980-85 1986-89 1990-92 Figure 5.5. Trout remeandered reach. The reason for this is In the period before and after the 30% 47% 51% Satisfactory abundance in that good habitats rapidly developed in remeandering of Gelså stream in 1989, trout population watercourses the regulated reach as a result of the the macroinvertebrate fauna was designated as cessation of weed clearance, while in the monitored in both the remeandered reach 30% salmonid spawning newly excavated remeandered reach, the and in an upstream still channelized reach 21% and nursery waters weeds first needed time to become (1). The year following remeandering, the 22% Sparse trout 40% population in Ribe County (6). established. macroinvertebrate fauna was 32% 27% No trout When assessing the impact of reme- impoverished in the remeandered reach population andering, one has to take into account compared with the reference reach the fact that the remeandered reach is (Figure 5.6). This was probably because of longer that the channelized reach it the unstablemorphological conditions Much remains to be achieved before all replaced. There is therefore actually room discussed above. By 1991, however, both watercourses fulfil the quality objectives, for many more habitats, and hence a macroinvertebrate density and species though. greater number of trout. In the case of number had increased considerably in the Idom stream, the new reach was twice as remeandered reach as compared with the Habitats for trout long as the former channelized reach. reference reach. Bypass riffles around preserved obstruc- Remeandering watercourses enhances tions not only permit free passage for fish Habitats for stream the variation in current and water depth and stream macroinvertebrates, but may macroinvertebrates and increases bank area. This creates also provide good habitats for trout. The laying out of stones and gravel in habitats for a more varied and abundant Investigations of the trout population in watercourses not only benefits the fish, macroinvertebrate fauna. Thus while the newly established riffles and bypass but also provides new habitats for the number of macroinvertebrate species in reaches in Vejle County show that there is macroinvertebrates that inhabit such a the two reaches of Gelså stream was often a markedly larger population in substratum. In Aarhus County, a marked almost equal prior to remeandering, there riffles and bypass reaches than in the increase has been registered in the so- were 30% more species in the remeande- upstream and downstream reaches (7). called “stone fauna” in watercourses red reach after two years (1). The reason is probably better physical where stones and gravel have been laid The population of stone fauna such as conditions in the form of hiding places out. The same has been seen in cases Heptagenia sulphurea also increased and current breakers, as well as the fact where changed weed clearance practice markedly in the remeandered reach of that the stones laid out ensure a good keeps the bed free of mud and sand. Gelså stream relative to the more unstable food resource with a rich population of and sandy reference reach (8). Moreover, macroinvertebrates. 12 a marked increase in the number of Remeandered When Idom stream was remeandered macroinvertebrates inhabiting stable beds Reference 9 (see Chapter 3.5) the trout population in ) was also seen within a year of remeande- 3 the remeandered reach three years after ring a reach of the river Brede. remeandering was just as large as in an 6 The increased abundance of macro- unregulated downstream reference reach, invertebrates in Gelså stream and the which already had a satisfactory trout Number (10 3 river Brede following remeandering is also population. However, remeandering per partly attributable to a change in the se does not necessarily mean the sudden composition of the vegetation. Thus 0 availability of better habitats for trout species such as the bur reed (Sparganium compared with those in a channelized emersum), which thrive on a soft bed reach. Good habitats can also be created Figure 5.6. with a weak current, are being replaced 50 in the channelized reach by switching to Macroinvertebrate by species such as the water starwort more environmentally sound maintenance abundance and (Callitriche sp.) and water crowfoot practice. Thus during the same period, species number in (Batrachium sp.). The latter species provide 25

the trout population of an upstream still the remeandered No. of species good habitats for many different macro- channelized reach of Idom stream also and reference invertebrates, whereas the filamentous increased markedly, and in the first years reaches of Gelså leaves of the bur reed almost only provide 0 was actually greater than in the newly stream (1). 1989 1990 1991 a suitable habitat for the buffalo gnat. 83 Environmental impact of watercourse rehabilitation

400 relatively flat riffle provides better habitats Reference reach Remeandered (upper) and possibilities for spawning. That many Remeandered (lower) other fish than trout are able to pass a correctly constructed bypass riffle is ) 300 -2 demonstrated by investigations of the river Storå bypass riffle at Holstebro, which has an average slope of 10‰ (9) 200 (Table 5.2). On the other hand, investigations have shown that it is usually only the strongest swimmers such as salmon and trout that

Plant biomass (g DW m 100 are able to pass through fish ladders, whereas weak swimmers such as the salmonid fish the lavaret are not quite able to do so. The selective effect of fish 0 ladders with respect to various fish species May May Jun Jul Aug Oct Dec Mar May Jun Jul Aug is one of the reasons why we in Denmark 1989 1990 1991 prefer to establish riffles and bypass Effects on the plant community Figure 5.7. Aquatic dominated by herbaceous plants to one reaches rather than fish ladders. Another After a watercourse has been macrophyte dominated by grasses. The latter benefit reason is that fish ladders require con- remeandered, it takes some time before biomass in the from the new riparian areas that flood siderable supervision and maintenance as the new vegetation in the watercourse reference reach and during the winter and the slower current they can easily be blocked by branches, achieves the same coverage as prior to the lower and in the newly created zones near the banks. remeandering. In Gelså stream, it took upper parts of the Because of Gelså stream’s new meanders two years for aquatic macrophyte biomass remeandered reach with the great variation in current condi- Table 5.2. Number of fish that passed the to reach the level in the reference reach of Gelså stream (1). tions, habitats have become available both bypass riffle in the river Storå at Holstebro (Figure 5.7). In Idom stream, it took up to for species that prefer flowing water, and over a 90-day period during the second half three years before vegetation coverage as for marsh plants as well as for species of 1991 (9). reached a level corresponding to that in that normally grow in more dry areas. the reaches that were not remeandered. Monitoring of Gelså stream following Species No. remeandering in 1989 also shows that Type 2: Restoration of Bream 536 after two years, a more diverse plant continuity between Dace 146 community had developed in the remean- watercourse reaches Eel 63 dered reach that was comprised of 30 Flounder 28 species, as compared with 22 species in Passage for migratory fish Grayling 21 the upstream channelized reference reach The investigations undertaken by Vejle Gudgeon 8 (1). The increase in species diversity is County of the fish populations in newly Lavaret 4,695 primarily attributable to species of established riffles and bypass reaches Perch 108 Pike 41 terrestrial vegetation and species known have shown that fish are even able to Rainbow trout 2 to be frequent in the seed bank, and pass steep riffles of up to 20–30‰, River lamprey 3 which easily germinate on the temporarily provided that they are able to find shelter Roach 436 vegetation-free banks, e.g. Juncus from the current behind stones and the Ruffe 63 articulatus, J. bufonius, Rumex suchlike (7). Moreover, it is not just strong Salmon 8 obtusifolius, Ranunculus sceleratus and swimmers such as trout that are able to Sea lamprey 5 Carex pseudocyperus. pass, but also weaker swimmers such as Sea trout 3 Tench 2 Compared with conditions in the theroach. In order to be on the safe side, Trout 4 stream prior to rehabilitation and those in however, such bypass riffles should not the reference reach, the plant community slope more than 10‰. This provides the Total 6,174 on the riparian areas changed from one best conditions for passage and the 84 Environmental impact of watercourse rehabilitation etc. On the other hand, though, it can 1871 water and its content of nitrogen and still be necessary to establish fish ladders iron compounds. We now know that if there is insufficient space to establish a riparian areas posses a natural potential riffle or a bypass reach. for removing nitrate-nitrogen by denitrifica- Culverts often act as an obstruction to tion (11). This removal capacity is lost or migratory fish. However, there is an reduced when the meadows are no example from Vejle County of trout being longer flooded, and instead the nitrogen able to pass a culvert providing the current is transported by the watercourse directly is not too great (10). The investigation to lakes and the sea. Moreover, in cases was carried out in Truds stream, where where lowering the water table exposes the stream runs through a 68 metre long iron-rich soils to the air, ochre loading will culvert under a motorway. The slope in increase. 1987 the culvert was so great and the current As a consequence of the lower ground- so strong that sea trout migrating water table in riparian areas following upstream to spawn were stopped at the watercourse channelization and deepening, culvert outlet. They were unable to swim the organic matter deposited as peat through the culvert and had therefore to becomes exposed to air and starts to lay their eggs downstream of the culvert. decompose. Over the years, this has led As a result, the spawning grounds the ground level to sink in many riparian became so overfull of eggs that only a areas with peaty soil. Extreme cases have small percentage survived. The reach been recorded where the ground level downstream of the culvert thus had 0 5 10 km has fallen 1–2 metres during a relatively insufficient carrying capacity for all the short period of 20–30 years. trout that migrated up to spawn. The Figure 5.9. Meadows and marshland in the lower part of the Decomposition of the peat results in County solved the problem by damming Skjern river system in 1871 and 1987. Major drainage in the 1960s the release of large amounts of nitrogen up the water in the culvert by means of a transformed approx. 4,000 ha of meadow and marshland to and phosphorus. Moreover, in areas with simple dam that could easily be passed by arable land. pyrite deposits large amounts of dissolved iron are also released which precipitates 20 the trout. This changed the current out in the watercourses as ochre. Before conditions so much that the trout were When one rehabilitates the water- 15 once again able to swim through the course by raising the water table again 10 culvert. In the subsequent spawning and enabling the watercourse to flood its 5 season, the spawning grounds upstream meadows, one to a greater or lesser of the culvert were also utilized, and over- extent recreates the original conditions. 0 After utilization of the downstream spawning Close contact is then restored between 45 grounds ceased. As a result, considerably the watercourse and its river valley. ) -2 more eggs and fry survived, the carrying 40 capacity of the stream having been better Effects on nutrient and organic 35 utilized (Figure 5.8). matter turnover and retention 30 Greater hydrological contact between a watercourse and its river valley leads to 25 Type 3: Rehabilitation of Trout (no.100 m Figure 5.8. Number improvements in biological conditions 20 and size distribution river valleys and watercourse quality, but also plays The objective of former channelization of animportant role with regard to the 15 of trout in Truds stream before and watercourses was to lower the water capacity of the system to even out water 10 after passage was table in the riparian areas in order that and sediment input, especially under 5 opened to addi- they could be cultivated. In addition to conditions of extreme precipitation and tional upstream Denmark having lost much of its wetlands runoff. Better hydrological contact with 0 0 5 10 15 20 25 30 35 spawning grounds (Figure 5.9), channelization has also had a the possibility to flood the riparian areas Total length (cm) (10). negative effect on the quality of the during periods of high discharge can 85 Environmental impact of watercourse rehabilitation increase the retention time of the water, exceeds the natural production of organic thereby limiting extreme discharge River valley Turnover of nitrate-N matter, there is the risk that phosphorus events. This helps reduce the risk of and wetland type: (kg ha-1 yr-1) and dissolved iron will be released from flooding further downstream, where the the former arable soil when anoxic riparian areas are often lower-lying. In Stevns stream (wet meadow) 57 conditions are restored. addition, flooding results in considerable Rabis brook (wet meadow) 98 retention and deposition of sediment in Voldby brook (meadow) 140 Effects on the river valley flora the river valley (Table 5.3) (12). Voldby brook (bog) 875 A higher water table can be demonstrated Rehabilitation projects involving raising Søbyvad stream (wet meadow) 590 by, among other things, investigating the the water level in the watercourse and Gjern stream (wet meadow) 42 plant community in the river valley. When increasing the frequency of flooding the Gelså river valley was mapped out reduce the nitrogen loading problem prior to remeandering in 1989, eight because of the natural capacity of wet Table 5.4. Turnover per hectare wetland in the river valley. areas were found with Glyceria maxima, riparian areas to remove nitrate-nitrogen of nitrate-nitrogen The expected reduction in nitrate loading which is one of the plant species indica- by denitrification (11) (Table 5.4). Such in wet and water- of the remeandered reach thus tive of areas where groundwater seeps to rehabilitation projects also raise the logged meadows materialized. the surface. In 1992, Glyceria maxima groundwater table in the adjacent riparian and bogs alongside Rehabilitation projects that lead to was found in 10 areas and in larger areas, as was the case when Gelså stream selected Danish more frequent flooding of riparian areas quantities than in 1989. Its growing in southern Jutland was remeandered. watercourses (11). also have other positive effects. Thus large presence thus indicates a general rise in Raising the watercourse bed and reducing amounts of phosphorus can sediment out the groundwater table in the river valley. its cross-sectional area increased the on the riparian areas together with fine Already before fixing the new path in water depth in the stream and the particulate matter during flooding. This watercourse remeandering projects, one groundwater table in the adjacent riparian has been demonstrated in the Gjern river needs to decide whether or not the areas, thereby restoring the anoxic valley, where up to 50 kg phosphorus former path of the watercourse should be conditions necessary for denitrification in sedimented out on 0.5 ha flooded meadow followed exactly. During the time that the the peat layer. This was expected to over a winter period encompassing 6–7 watercourse has been channelized, eventually reduce diffuse nitrate loading flood events. valuable new habitats might have arisen of the stream. During excavation work in In connection with the remeandering that have potential as future dispersal summer 1989, though, nitrate loading of of Rind stream, Ringkjøbing County areas. One therefore needs to assess the rehabilitated reach exceeded that of showed that effective ochre removal whether it is possible to preserve them, or the upstream channelized reaches. could be obtained by letting the stream whether they can be re-established in the However, measurements made the water flow over the meadow during the river valley following completion of following two summers gave the opposite winter period (see Chapter 3.6). The stream excavation work. The removal of result, annual nitrogen loading having has been dimensioned such that the important habitats cannot always be fallen by approx. 80 kg nitrate-nitrogen surrounding meadows flood at the normal avoided, however. When Gelså stream winter discharge in the stream. It is also was remeandered, the new course Table 5.3. Mean accumulation rate of sediment and total phos- at this time that leaching of ochre from followed many of the former meanders. phorus at approx. 5,000 m2 of temporarily flooded meadow land the catchment is greatest. A number of The majority of these were inhabited by in the lower part of Gjern stream during three flooding events in shallow basins with a grass bed have more plant species than was average for winter 1992-93 (12). been made on the meadow. The dissolved the river valley, especially wetland species and particulate iron in the stream water (1). Nevertheless, despite the removal of precipitates out in the basins such that several wetland communities a more Period No. Accumulated Accumulated the water leaving the meadow is characteristic wetland vegetation had of sediment phosphorus considerably cleaner than that entering established itself in the river valley already -2 -2 days (kg m ) (g P m ) the meadow. within two years of remeandering. There are also risks associated with 24 Nov - 2 Dec 1992 8 0.26 1.18 restoring former cultivated riparian areas Effects on the river valley fauna 11 Jan - 20 Jan 1993 9 1.21 3.78 to wetlands, however. Thus in cases where When a dry meadow is transformed to a 21 Jan - 9 Feb 1993 19 3.02 6.54 the amount of nitrate-nitrogen that has wetland, conditions for the fauna will to be denitrified in the riparian areas change. Which species will dominate 86 Environmental impact of watercourse rehabilitation depends on how the area develops. This Figure 5.10. can be illustrated by an example from Distribution of West Stadil Fjord (14), a partly reclaimed ecosystem types in low-lying wetland area adjacent to Stadil West Stadil Fjord at Fjord. Even though it is not a water- four different water

course, the example illustrates the levels relative to sea West Stadil Fjord West Stadil Fjord West Stadil Fjord West Stadil Fjord general possibilities for changing habitat level: Unchanged - conditions for fauna. 1.4 m, -1.0 m, -0.4 m The expected impact on this drained and +0.2 m (corre- wetland ecosystem of four alternative sponding to the water table levels is illustrated in Figure level in Stadil Fjord) 5.10. In the first alternative, the water (14). table is unchanged relative to the current drained level, and is nearly 1.5 metre below sea level. This provides good possibilities for agriculture and good conditions for the many thousand geese that rest here each spring and autumn. In -1.40 m -1.00 m -0.40 m +0.20 m the second alternative with a higher Open water Reed beds Meadow Arable land water table, many of the fields will be too wet to be cultivated. The geese will still perhaps with additional supplementary therefore be followed up by investigations be able to thrive and conditions will measurements. Surveys of the benthic of whether the eggs survive, hatch and improve for ducks and wading birds. In macroinvertebrate and/or fish fauna will produce adult trout. the third alternative with an even higher in most cases be sufficient to provide the With regard to major changes to the water table, reed beds will spread and the necessary documentation. path or form of watercourses, considerable agricultural areas and the meadows will The examples of impact assessment knowledge has been accumulated in almost disappear. Wading birds and geese studies that are presented in this book are Denmark through integrated physical, will loose their feeding grounds but on from several points of view insufficient to chemical and biological investigations in the other hand, good habitats will arise allow evaluation of the value to nature selected projects. We thus know that for bitterns and other birds that inhabit and the environment of the rehabilitation projects of this type create greater reed beds. All three alternatives require projects undertaken in Denmark. On the physical and hence biological diversity. continued pumping of water out of the other hand, there are also many results Our knowledge is nevertheless still area. In the final alternative, in which that unambiguously indicate that the insufficient because the investigations pumping is ceased completely, the water types of rehabilitation project currently have usually only been undertaken over a table is 0.2 metre above sea level and a being undertaken live up to expectations. short period after completion of rehabili- lake forms surrounded by reed beds. The Our knowledge of the impact of type 1 tation. Thus the impact assessment area’s most important function is as a projects i.e. those designed to rehabilitate studies are usually undertaken during the stopover for birds on the open surface of watercourse reaches by remeandering, period when the watercourse is still being the water. constructing a two-step cross-sectional colonized by flora and fauna, and when profile, opening culverted reaches, physical adjustments are still taking place The need for impact assessment establishing spawning grounds for in the direction of dynamic equilibrium. studies salmonids, etc., is in some respects Ideally, one should therefore repeat the With most types of rehabilitation project, insufficient. While there is no doubt that studies after a couple of years. it is necessary to undertake a certain we are now able to establish good The results of the studies undertaken minimum amount of monitoring as a spawning grounds that are in fact utilized at Idom stream indicate that an optimal form of documentation to the general by trout, they often become silted over trout population can become established public and to benefit the planning of with sand or finer material because of within three years of a reach being future projects. Such a basic programme excessive sediment input to the water- remeandered (see Chapter 3.5). With will usually make use of the existing course from the surroundings. Establish- regard to macroinvertebrates, there are environmental monitoring programme, ment of spawning grounds should other examples of the very rapid establish- 87 Environmental impact of watercourse rehabilitation

Rehabilitation project Physical Chemical Fish Macroinverte- Plants Birds Other Recreative effects effects effects brates/insects animals uses

Type 1: Rehabilitation of + ++ + + + 0 0 ++ watercourse reaches

Type 2: Restoration of continuity 0 0 + + 0 0 + ++ between watercourse reaches

Type 3: Rehabilitation of river valleys ++ +++ - +++ ++ ++ +++ +++

0: No effect likely. +: Knowledge exists or is forthcoming, but the element should be included in basic impact monitoring studies. ++: Only partial knowledge is available, and the element should be included in new impact monitoring studies. +++: No knowledge is available, and the element should be included in selected projects.

ment of a fauna appropriate to the Table 5.5. Areas and is most difficult and costly to assess. When planning impact assessment habitat conditions pertaining. Thus if topics for which Moreover, it can take many years for such studies, one has to differentiate between stones are laid out, they will be rapidly knowledge of the projects to take effect fully. Some impact areas where knowledge is presently colonized by macroinvertebrates that impact of the assessment projects have been initiated in insufficient, and areas where it is conside- prefer stony substrata. A precondition, various types of Denmark in connection with the rehabili- red that sufficient information is available though, is that there is a population rehabilitation tation of riparian areas. Examples are the to be able to assess the value and nearby. This occurs most rapidly when the project in Denmark remeandering of the river Brede in possible risks of rehabilitation projects. macroinvertebrates are present in upstream is lacking. southern Jutland and the remeandering Where knowledge is lacking or or downstream reaches, although stream of the upper reach of the river Gudenå inadequate, detailed studies of the topic insects can also fly in from other water- (15). The results of these studies will first should be undertaken in connection with courses. be available in the coming years. general monitoring in a few specially The type of rehabilitation projects In the future, there is a particular need selected projects. In the case of areas about which we know most are the type 2 to collect experiences from suitable wheresufficient knowledge is already projects, which aim to restore free rehabilitation projects that can supple- available, a basic monitoring programme passage between watercourse reaches. ment already existing knowledge – not can be undertaken as a natural part of An example is modern fish passes, which only from Denmark, but also from the normal watercourse supervision. In Table are constructed in the form of riffles or rest of Europe. This applies both to 5.5, we have attempted to summarize the bypass reaches. In this case, impact methods and to geographical conditions. areas and topics where Denmark currently assessment studies have shown that fish With respect to the Danish projects lacks knowledge of the impact of the really can pass them. However, even if aimed at rehabilitating riparian areas, various types of rehabilitation project. fish and macroinvertebrates can pass the experience is in most cases lacking as to former obstructions, the biological both the hydrological effects and the objective of removing the obstruction is effects on the turnover, retention and not fulfilled if upstream habitat conditions possible release of nutrients, iron, are unsuitable for them, or if they are sulphate, etc. In addition, studies of their unable to wander freely in the upstream impact on animals and plants are also reaches. lacking, as are studies of the utility value The type 3 rehabilitation projects, of the projects. In the coming years, it is which aim to rehabilitate the riparian therefore necessary to establish further areas (the river valley), are those about large-scale demonstration projects which we know least. At the same time, encompassing integrated monitoring. they are often the projects whose impact 88 Environmental impact of watercourse rehabilitation

References to Chapter 5 1 Kronvang, B., Græsbøll, P., Svendsen, L.M., 9 Jørgensen, J. (1993): Fish passage at Friberg, N., Hald, B., Kjellson, G., Nielsen, Holstebro hydroelectric power station (in M.B., Petersen, B.D. & Ottosen, O. (1994): Danish). – Vand & Miljø 1: 13- 17. Restoration of Gelså stream at Bevtoft – 10 Kristiansen, H.R. (1994): Free passage for Environmental impact on the watercourse trout restored in Truds stream (in Danish). – and riparian areas (in Danish). – Technical Vand & Jord 2: 77-79. Report No. 110, National Environmental Research Institute. 87 pp. 11 Kronvang, B., Hoffmann, C.C., Iversen, T.M., Jensen, J.J., Larsen, S.E., Platou, S.W. & 2 Græsbøll, P., Aub-Robinson, C. & Kronvang, Skop, E. (1994): Nitrogen loading of B. (1988): Establishment of spawning Limfjorden fjord (in Danish). – Tema-rapport grounds in watercourses (in Danish). – No. 1, National Environmental Research Technical Report No. 22, Freshwater Institute. 16 pp. Laboratory, Danish Environmental Protection Agency. 75 pp. 12 Aub-Robinson, C., Falkum, Ø., Hansen, C.D., Svendsen, L.M. & Kronvang, B. (1996): 3 Larsen, K.H. & Henriksen, P.W. (1992): Sand Retention of particulate matter and migration destroys trout eggs (in Danish). – associated nutrients in aquatic macrophytes Vand & Miljø 6: 188-192. and on flooded riparian areas. – In: 4 Sivebæk, F. & Bangsgaard, L. (1995): Kronvang, B., Sibbesen, E. & Svendsen, L.M. Sediment on trout spawning grounds (in (eds.): Erosion and delivery, transport and Danish). – Vand & Jord 6: 258-261. fate of sediments and sediment-associated 5 Bangsgaard, L. & Sivebæk, F. (1996): What nutrients in watersheds. – Proceedings of a habitats do trout fry prefer? (in Danish) – workshop, 9-12 October 1995, Silkeborg, Vand & Jord 1. Denmark. National Environmental Research Institute. 6 Ejbye-Ernst, M. (1993): Watercourse fish populations (in Danish). – Ribe County, 13 Madsen, B.L. (1995): Danish Watercourses – Technical and Environmental Department. Ten years with the new Watercourse Act: 39 pp. Collected examples of maintenance and restoration. – Environmental News No. 11, 7 Bangsgaard, L. (1993): Fish density in 14 Danish Environmental Protection Agency. riffles and bypasses in Vejle County (in 206 pp. Danish). – Vejle County Council. 41 pp. 14 Degn, H.J. (1990): We choose our nature 8 Friberg, N., Kronvang, B., Svendsen, L.M., ourselves (in Danish). – Vand & Miljø 4: 134- Hansen, H.O. & Nielsen, M.B. (1994): 136. Restoration of a channelized reach of Gelså stream, Denmark: effects on the macro- 15 Hansen, H.O. (in press): Remeandering of a invertebrate community. – Aquatic Conser- Danish headwater stream: The river Gudenå vation: Marine and Freshwater Ecosystems demonstration project. – Internat. Verein. 4: 289-296. Limnol.

89 Appendix A

Suggestions for a questionnaire When filling out the questionnaire, one In the case of type 2 rehabilitation should always bear in mind the primary projects – Restoration of continuity objective of the rehabilitation project. between watercourse reaches – the Four levels need be considered: project has to create free passage to at least 1 km of upstream watercourse to be . The first level describes the project considered a project. Thus if there are, for type. Only one of the three types may example, five obstructions over a 1 km be selected. Each type has its own reach, removal of one of the obstructions questionnaire (Forms A.1, A.2 and A.3 is not considered a rehabilitation project are examples of how to fill out the that should be included in the statistics questionnaires). until all five obstructions have been . The second level describes the primary removed, and then only as one single method. Only one primary method project. In the above example, the project shall be selected under each project is not considered to have been completed type. until all the obstructions have been . The third level describes the secondary removed, not even if there is a delay of methods. Several secondary methods several years between the removal of the may be selected, but they should not first and last falls. Similarly, the reopening be assigned any order of priority. Note of culverted reaches does not count as a that in some cases there are no rehabilitation project unless it creates free secondary methods, but only a primary passage to at least 1 km of upstream method. watercourse. . The fourth level describes the In the following, three examples are elements used in the rehabilitation given of how the questionnaire should be project. Several elements may be filled out. Note that we have not yet selected, but they should not be completed the final design of the assigned any order of priority. Note questionnaires and the database. that in some cases there are elements but no secondary methods. 91 Appendix A

Type 1 example (Form A.1): A reach of a Type 2 example (Form A.2): A reach of a Type 3 example (Form A.3): It is wanted watercourse passing through a forest is watercourse is culverted. It is wanted to to enable a watercourse to flood adjacent culverted. Prior to being culverted, the open the reach to enable trout to migrate meadows in the hope of reducing the reach was inhabited by three rare species to upstream spawning grounds. The nitrogen content of the water. This is of caddis flies. It is wanted to recreate reach is remeandered with a two-step achieved by narrowing the watercourse habitats for these three species by cross-sectional profile. Stones and gravel and terminating the drains in the meadow reopening the culverted reach. At the beds are laid out and trees are planted rather than in the watercourse. In addition, same time, the reach is to be remeandered along the banks. a culverted reach of the watercourse is to along its original course. In addition, the As the main objective is to restore free be opened and a two metre high falls is fir trees that were planted along the passage, the project falls in under type 2 to be replaced by a riffle of stones. Finally, watercourse after it had been culverted Restoration of continuity between a pond is to be established in the meadow are to be removed and replaced with the watercourse reaches. and the water is to be led through an natural vegetation of elm trees. The primary method is 30 – Culverted ochre sedimentation basin. The rehabilitation project falls in under reach opened to create free passage, The main objective in this example is type 1 – Rehabilitation of watercourse while the secondary methods are 51 – to enable the watercourse to flood the reaches – since the main objective is to Reach remeandered and 53 – Two-step meadows, and the project thus involves create habitats locally in the watercourse. cross-sectional profile created. The the whole river valley. The rehabilitation Despite the fact that removal of the elements used in the project are 76 – project therefore falls in under type 3 – culvert also creates free passage between Stones laid out, 77 – Gravel laid out Rehabilitation of river valleys. That free the downstream and upstream reaches and 82 – Trees and bushes planted passage is created between two water- that is not the main objective, and the within the 2 metre cultivation-free course reaches by reopening the culvert is project cannot be classified as a type 2 border zone. a side benefit of the rehabilitation project. rehabilitation project. The primary method is 6 – Water As the main objective is to open the In the database the rehabilitation project table and flooding frequency increased culvert, the primary method is therefore is therefore recorded as 2/30/51–53/76– by narrowing the watercourse, while 52 – Culverted reach opened to create 77–82, or as follows: the secondary methods are 3 – Water better habitats. Although remeandering table and flooding frequency of the reach is part of the project, it will increased by terminating drains in not be undertaken without removal of Project Primary Secondary Elements meadows, 8 – Lakes/ponds/wetlands the culvert and 51 – Reach remeandered type method methods etc. established in the river valley, is therefore a secondary method. 230517626 – Obstruction replaced by riffle, 30 In addition, the project includes 53 77 – Culverted reach opened to create element 83 – Trees and bushes remo- 82 free passage and 56 – Ochre sedimen- ved within the 2 metre cultivation- tation basin established in connection free border zone and element 82 – with the watercourse. As the riffle was Trees and bushes planted within the 2 made of stones, the project involved metre cultivation-free border zone. element 76 – Stones laid out.

In the database, the rehabilitation project In the database, the rehabilitation project is therefore recorded as 1/52/51/82–83, is therefore recorded as 3/6/3–8–26–30– or as follows: 56/76, or as follows:

Project Primary Secondary Elements Project Primary Secondary Elements type method methods type method methods 1525182 36 3 76 83 8 26 30 56

92 Appendix A

Form A–1. Example of a type 1 rehabilitation project (see “Suggestions for a questionnaire” above).

Type 1: Rehabilitation of watercourse reaches

Watercourse: Vridsted brook Location (town/district): Vridsted Watercourse system: River Karup County/Municipality (code): 07/105 Coordinates: 56° 27´ N 9° 02´ E Rehabilitation completed (year): 1995 Total cost (excl. VAT): DKK 350,000 Length of rehabilitated reach (m): 750 Upstream catchment area (km2): 21 Discharge in the rehabilitated reach (l/s): Mean: 10 Max: 16 Min: 5

Primary Secondary Elements method methods One cross Several crosses Several crosses

51 Reach remeandered x 52 Culverted reach opened to create better habitats 53 Two-step cross-sectional profile created 54 Designated as a maintenance-free natural watercourse 55 Lakes established/re-established in connection with the watercourse 56 Ochre sedimentation basin established in connection with the watercourse 57 Single measures 58

x 51 Reach remeandered 52 Culverted reach opened to create better habitats 53 Two-step cross-sectional profile created 54 Designated as a maintenance-free natural watercourse 55 Lakes established/re-established in connection with the watercourse 56 Ochre sedimentation basin established in connection with the watercourse 57 --- 58

76 Stones laid out 77 Gravel laid out 78 Artificial fish hiding places established 79 Other solid objects laid out 80 Current concentrators established 81 Sand trap constructed x 82 Trees and bushes planted within the 2 metre cultivation-free border zone x 83 Trees and bushes removed within the 2 metre cultivation-free border zone 84 Artificial bed and/or bank established (fascines, concrete, paving slabs, etc.) 85 Artificial bed and/or bank removed (fascines, concrete, paving slabs, etc.) 86 93 Appendix A

Form A–2. Example of a type 2 rehabilitation project (see “Suggestions for a questionnaire” above).

Type 2: Restoration of continuity between watercourse reaches

Watercourse: Vester Bybæk brook Location (town/district): Slagelse Watercourse system: Tude stream County/Municipality (code): 04/189 Coordinates: 55° 24´ N 11° 23´ E Rehabilitation completed (year): 1995 Total cost (excl. VAT): DKK 350,000 Length of rehabilitated reach (m): 325 Upstream catchment area (km2): 102 Discharge in the rehabilitated reach (l/s) Mean: 35 Max.: 70 Min.: 19

Primary Secondary Elements method methods One cross Several crosses Several crosses

26 Obstruction replaced by riffle 27 Obstruction replaced by meanders 28 Bypass riffle established at preserved obstruction 29 Riffle established at preserved obstruction x 30 Culverted reach opened to create free passage 31 Culvert falls evened out (drop manhole removed, etc.) 32 Greater water depth and/or current breakers in underpass culverts 33 Falls evened out at culvert outlet/bridge 34 Fish ladder/fish sluice established 35 --- 36 Formerly periodically “dried-up” stream reach completely restored 37 Formerly periodically “dried-up” stream reach partly restored 38 Water pumped into watercourse to keep open “dried-up” reach 39 --- 40 --- 41

26 Obstruction replaced by riffle 27 Obstruction replaced by meanders 28 Bypass riffle established at preserved obstruction 29 Riffle established at preserved obstruction 30 Culverted reach opened to create free passage 31 Culvert falls evened out (drop manhole removed, etc.) 32 Greater water depth and/or current breakers in underpass culverts 33 Falls evened out at culvert outlet/bridge 34 Fish ladder/fish sluice established 35 Fish ladder/fish sluice removed 36 Formerly periodically “dried-up” stream reach completely restored 37 Formerly periodically “dried-up” stream reach partly restored 94 Appendix A

Type 2 – continued

Primary Secondary Elements method methods One cross Several crosses Several crosses

38 Water pumped into watercourse to keep open “dried-up” reach 39 Otter pass established 40 Free passage established for other vertebrates 41 x 51 Reach remeandered 52 Culverted reach opened to create better habitats x 53 Two-step cross-sectional profile created 54 Designated as a maintenance-free natural watercourse 55 Lakes established/re-established in connection with the watercourse 56 Ochre sedimentation basin established in connection with the watercourse 57 --- 58 59

x 76 Stones laid out x 77 Gravel laid out 78 Artificial fish hiding places established 79 Other solid objects laid out 80 Current concentrators established 81 Sand trap constructed x 82 Trees and bushes planted within the 2 metre cultivation-free border zone 83 Trees and bushes removed within the 2 metre cultivation-free border zone 84 Artificial bed and/or bank established (fascines, concrete, paving slabs, etc.) 85 Artificial bed and/or bank removed (fascines, concrete, paving slabs, etc.) 86 87

95 Appendix A

Form A–3. Example of a type 3 rehabilitation project (see “Suggestions for a questionnaire” above).

Type 3: Rehabilitation of river valleys

Watercourse: Egebæk brook Location (town/district): Ringe Watercourse system: River Odense County/Municipality (code): 02/094 Coordinates: 55° 14´ N 10° 30´ E Rehabilitation completed (year): 1995 Total cost (excl. VAT): DKK 350,000 Length of rehabilitated reach (m): 2500 Upstream catchment area (km2): 135 Discharge in the rehabilitated reach (l/s) Mean: 75 Max: 105 Min: 50

Primary Secondary Elements method methods One cross Several crosses Several crosses

1 Water table and flooding frequency increased by remeandering the watercourse 2 Water table and flooding frequency increased by raising the bed 3 Water table and flooding frequency increased by terminating drains in meadows 4 Water table and flooding frequency increased by establishing a dam 5 Water table and flooding frequency increased by meadow trickling x 6 Water table and flooding frequency increased by narrowing the watercourse 7 --- 8 --- 9 --- 10 11

1 Water table and flooding frequency increased by remeandering the waterurse 2 Water table and flooding frequency increased by raising the bed x 3 Water table and flooding frequency increased by terminating drains in meadows 4 Water table and flooding frequency increased by establishing a dam 5 Water table and flooding frequency increased by meadow trickling 6 Water table and flooding frequency increased by narrowing the watercourse 7 Lakes/ponds/wetlands etc. re-established in the river valley x 8 Lakes/ponds/wetlands etc. established in the river valley 9 Vegetation management in the river valley 10 11

96 Appendix A

Type 3 – continued

Primary Secondary Elements method methods One cross Several crosses Several crosses

x 26 Obstruction replaced by riffle 27 Obstruction replaced by meanders 28 Bypass riffle established at preserved obstruction 29 Riffle established at preserved obstruction x 30 Culverted reach opened to create free passage 31 Culvert falls evened out (drop manhole removed, etc.) 32 Greater water depth and/or current breakers in underpass culverts 33 Falls evened out at culvert outlet/bridge 34 --- 35 Fish ladder/fish sluice removed 36 Formerly periodically “dried-up” stream reach completely restored 37 Formerly periodically “dried-up” stream reach partly restored 38 Water pumped into watercourse to keep open “dried-up” reach 39 Otter pass established 40 Free passage established for other vertebrates 41 42 51 Reach remeandered 52 Culverted reach opened to create better habitats 53 Two-step cross-sectional profile created 54 Designated as a maintenance-free natural watercourse 55 Lakes established/re-established in connection with the watercourse x 56 Ochre sedimentation basin established in connection with the watercourse 57 --- 58 59

x 76 Stones laid out 77 Gravel laid out 78 Artificial fish hiding places established 79 Other solid objects laid out 80 Current concentrators established 81 Sand trap constructed 82 Trees and bushes planted within the 2 metre cultivation-free border zone 83 Trees and bushes removed within the 2 metre cultivation-free border zone 84 Artificial bed and/or bank established (fascines, concrete, paving slabs, etc.) 85 Artificial bed and/or bank removed (fascines, concrete, paving slabs, etc.) 86 87

97 References

Ansbæk, J., Jensen, F., Schultz, K.E. & Aagaard, Græsbøll, P., Aub-Robinson, C. & Kronvang, B. P. (1981): The societal significance of (1988): Establishment of spawning grounds watercourses (in Danish). – Freshwater in watercourses (in Danish). – Technical Laboratory, Danish Environmental Protection Report No. 22, Freshwater Laboratory, Agency. Danish Environmental Protection Agency. 75 Aub-Robinson, C., Falkum, Ø., Hansen, C.D., pp. Svendsen, L.M. & Kronvang, B. (1996): Hansen, H.O. (in press): Remeandering of a Retention of particulate matter and Danish headwater stream: The river Gudenå associated nutrients in aquatic macrophytes demonstration project. – Internat. Verein. and on flooded riparian areas. – In: Limnol. Kronvang, B., Sibbesen, E. & Svendsen, L.M. Hunt, R.L. (1992): Evaluation of trout habitat (eds.): Erosion and delivery, transport and improvement structures in three high- fate of sediments and sediment-associated gradient streams in Wisconsin. – Technical nutrients in watersheds. – Proceedings of a Bulletin No. 179, Department of Natural workshop, 9-12 October 1995, Silkeborg, Resources, Madison. 210 pp. Denmark. National Environmental Research Institute. Jørgensen, J. (1993): Fish passage at Holstebro hydroelectric power station (in Danish). – Bangsgaard, L. (1993): Fish density in 14 riffles Vand & Miljø 1: 13- 17. and bypasses in Vejle County (in Danish). – Vejle County. 41 pp. Kristiansen, H.R. (1994): Free passage for trout restored in Truds stream (in Danish). – Vand Bangsgaard, L. & Sivebæk, F. (1996): What & Jord 2: 77-79. habitats do trout fry prefer? (in Danish) – Vand & Jord 1. Kronvang, B., Hoffmann, C.C., Iversen, T.M., Jensen, J.J., Larsen, S.E., Platou, S.W. & Brookes, A. (1984): Recommendations bearing Skop, E. (1994): Nitrogen loading of on the sinuosity of Danish stream channels. Limfjorden fjord (in Danish). – Tema-rapport – Technical Report No. 6, Freshwater No. 1, National Environmental Research Laboratory, Danish Environmental Protection Institute. 16 pp. Agency. 130 pp. Kronvang, B., Græsbøll, P., Svendsen, L.M., Degn, H.J. (1990): We choose our nature ourselves Friberg, N., Hald, B., Kjellson, G., Nielsen, (in Danish). – Vand & Miljø 4: 134-136. M.B., Petersen, B.D. & Ottosen, O. (1994): Ejbye-Ernst, M. (1993): Watercourse fish Restoration of Gelså stream at Bevtoft – populations (in Danish). – Ribe County, Environmental impact on the watercourse Technical and Environmental Department. and riparian areas (in Danish). – Technical 39 pp. Report No. 110, National Environmental Friberg, N., Græsbøll, P. & Larsen, S.E. (in press): Research Institute. 87 pp. Causes of the generally poor state of smaller Larsen, K.H. & Henriksen, P.W. (1992): Sand Danish watercourses (in Danish). – Environ- migration destroys trout eggs (in Danish). – mental Project, Danish Environmental Vand & Miljø 6: 188-192. Protection Agency. Madsen, B.L. (1995): Danish Watercourses – Friberg, N., Kronvang, B., Svendsen, L.M., Ten years with the new Watercourse Act: Hansen, H.O. & Nielsen, M.B. (1994): Collected examples of maintenance and Restoration of a channelized reach of Gelså restoration. – Environmental News No. 11, stream, Denmark: effects on the macro- Danish Environmental Protection Agency. invertebrate community. – Aquatic Conser- 206 pp. vation: Marine and Freshwater Ecosystems Nielsen, J. (1994): Fish passage at obstructions 4: 289-296. in Danish streams. – Vejle County. 9 pp. 98 Nielsen, J. (1995): Fish requirements as to watercourse physical condition – A selection of existing knowledge (in Danish with English summary). – Environmental Project No. 293, Danish Environmental Protection Agency. 129 pp. Osborne, L.L., Bayley, P.B. & Higler, L.W. (eds.) (1993): Lowland stream restoration: Theory and practice. – Freshwater Biology (special issue) 2: 187-342. Sivebæk, F. & Bangsgaard, L. (1995): Sediment on trout spawning grounds (in Danish). – Vand & Jord 6: 258-261. Thienemann, A. (1950): Die Verbreitungs- geschichte der Süsswassertierwelt Europas (in German). – Die Binnengewässer Band XVIII, Stuttgart. Wiberg-Larsen, P., Petersen, S., Rugaard, T. & Geertz-Hansen, P. (1994): Better water- course maintenance increases the number of fish (in Danish). – Vand & Jord 6: 263-265.

99 River Restoration Restoration of watercourses is currently attracting increasing attention throughout Europe, and considerable experience and know-how has been accumu- lated in Denmark over the last decade. – Danish experience and examples To benefit from this experience, the European Centre for River Restoration (ECRR) has recently been established at the National Environmental Research Institute in Silkeborg, Denmark.

The ECRR will eventually grow to encompass a network of relevant European institutions working with river restoration.

This handbook is the ECRR’s first, and aims to provide an insight into Danish experience with watercourse and river valley management and restoration.

Ministry of Environment and Energy National Environmental Research Institute