Mänsklig påverkan på mindre vattendrag i skogslandskapet
Interference in an ecosystem means a disturbance. When harvesting, forest roads have to be build to cope with heavy duty vehicles. Crossing brooks can not always be avoided. In this case bridges or culverts have to be built. There are many different kinds of culverts and depending on what type yo...
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| Formato: | Otro |
| Lenguaje: | sueco sueco |
| Publicado: |
2006
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| Materias: | |
| Acceso en línea: | https://stud.epsilon.slu.se/12421/ |
| Sumario: | Interference in an ecosystem means a disturbance. When harvesting, forest roads have to be
build to cope with heavy duty vehicles. Crossing brooks can not always be avoided. In this
case bridges or culverts have to be built. There are many different kinds of culverts and
depending on what type you choose and how you place the culvert, the watercourse and the
water organisms can be harmed in different ways. If you choose the best alternative and place
the culvert correctly, migration of aquatic living organisms is possible. Migration barriers can
be high velocity in the culvert, large jumping height from the brook or too small water depth
close to the culvert.
Forestry is carried out as effectively as possible. This can result in damaged
protection zones along the brooks. To leave protection zones means incurred costs.
Furthermore, it takes time to consider which trees to leave and the harvester may not see the
watercourse or may lack knowledge about the value of protection zones along streams.
I inventoried 118 culverts. Johan Spens at the Department for Aquaculture at
SLU in Umeå has developed a calculating model, the ecohydraulic model, which can predict a
culverts function and determine whether it is a possible migration barrier. I tested the model
by comparing it with two other models, System Aqua developed by the Swedish
Environmental Protection Agency and guidelines developed by the Swedish Fisheries
Agency. I could test all three different models at 21 culverts, comparing the results in respect
of whether the culverts were migration barriers. The ecohydraulic model calculated that 17
culverts was a migration barrier, the Fishery Agency's guidelines resulted in 18 barriers and
System Aqua in 10.
In comparison to System Aqua and the Swedish Fisheries Agency guidelines, I
conclude that the ecohydraulic model provides a realistic evaluation of the culvert function. It
also takes into consideration seasonal variations in water levels, thus providing information on
whether the culvert is under-dimensioned. Furthermore, the model is easy to use for persons
without aquatic – ecological competence. |
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