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