River Restoration

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 .

Load more