Difference between revisions of "Bouxweerd - Artificial pool"
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==Hydromorphological response== | ==Hydromorphological response== | ||
| + | ===Hydrological regime=== | ||
| + | The flooding frequency of the pool is determined by a step in the dam that separates the pool from the river. On average the pool is inundated more then 100 days per year. This leads to sedimentation of the pool. | ||
| + | |||
| + | ===River continuity=== | ||
| + | Unaffected | ||
| + | |||
| + | ===Morphological conditions=== | ||
| + | The major morphological change in the area is the sedimentation of the pool due to inundation. The banks of the river are all fixated, leading to a lack of sediment input and bank formation. Sedimentation on banks and the dikes only takes place during high water peaks. | ||
==Monitoring before and after implementation of the project== | ==Monitoring before and after implementation of the project== | ||
Revision as of 13:49, 25 May 2010
Bouxweerd - Artificial pool
Key features of the case study
Site description
The Bouxweerd area is situated on the floodplain of the canalized Meuse river. Most of the area has seen a good deal of mining of both clay and gravel. The gravel mining started as early as the 1940's. A part of the area was filled up with sand and debris after the gravel was extracted. A gravel pit was also left behind however; this filled up with water and serves as an artificial pool which is characteristic to the area. In the northern part of the area a small wetland forest is situated. The forest is fed by upwelling groundwater. A ditch which was used for the hydro management of the area for agricultural use is situated near this forest.
Measures selection
The large pool was dug for non-nature restorative reasons. It was a side-product of the economically profitable gravel mining. In 2003 measures were taken to ensure that the floodplain was inundated more often. A adjustable weir was installed in the ditch in 2003 to control the water flow from the wetland forest. Later on in 2008 it became apparent that the forest was still drying out and the ditch was closed off near the forest to avoid water loss. The weir was removed as it no longer served a function.
Success criteria
Not listed
Ecological response
Macrophytes and phytobenthos
A number of macrophytes were encountered in the river. In comparison to pre-project data there is an increase in macrophytes, however the overall results are disappointing. Research has shown that this is caused by the management choices in nearby grasslands which are aimed at geese. These geese graze on the macrophytes and thereby suppress both colonisation and development of a macrophyte community. The pool is devoid of macrophytes.
Benthic Invertebrates
No known data.
Fish
Fish were not monitored in the pool, however it is expected that it is not a suitable habitat for rare fish species. Some general fish are known to occur there. During summer the pool is known for fish dying due to anoxia and botulism.
Other biota
Dry land flora
The dry land flora has developed relatively poorly since the project started. The characteristic upwelling forest has shown no signs of development. This can be explained by nearby sand excavations that accidentally dug through a soil layer which led to the severing of the upwelling in the area. The large amount of grazing by birds does not help the floral development either.
Breeding birds
The area shows remarkably high numbers of breeding birds, both regular as well as a few rare species. The area, in comparison with other areas, has a high species richness and diversity. Even though the water quality of the pool is bad it still serves as a feeding ground for the breeding birds. The shallow parts of the pool are home to a large number of insects which serve as a food source for the birds.
Hydromorphological response
Hydrological regime
The flooding frequency of the pool is determined by a step in the dam that separates the pool from the river. On average the pool is inundated more then 100 days per year. This leads to sedimentation of the pool.
River continuity
Unaffected
Morphological conditions
The major morphological change in the area is the sedimentation of the pool due to inundation. The banks of the river are all fixated, leading to a lack of sediment input and bank formation. Sedimentation on banks and the dikes only takes place during high water peaks.
Monitoring before and after implementation of the project
Socio-economic aspects
Contact person within the organization
Extra background information
References
Related Measures
- Lower river banks or floodplains to enlarge inundation and flooding
- Reduce groundwater extraction
- Remove or modify in-channel hydraulic structures
- Set back embankments, levees or dikes
- Restore wetlands
