Issues of Catchment Management
- Catchment management is an holistic way of looking at a whole river catchment, its interaction between water and land and how best to manage and improve drainage
- The aim is to minimise flooding, drought, water pollution, channel erosion and improve ecosystems that rely on the river
- Decisions are made by local authorities and private engineers, usually without consultation with local residents, which generates conflict and resentment
- Catchment management schemes are disruptive and expensive
- Ecological balance is disturbed through increased water temperatures and waste water discharge
- Other issues include:
- Concentrated water pollution and spread of viruses
- Decreased water flow in dry periods impact aquatic ecosystems
- Increased flooding and erosion
- Management methods include:
- Soft engineering - using knowledge of river basin processes to work with nature
- Hard engineering - building structures to 'push back' against nature
Comparison of Soft and Hard Engineering Approaches to Urban Drainage Management
| Soft Engineering | Hard Engineering |
| Afforestation increases interception and reduces throughflow, along with surface runoff. EVT removes water that would eventually end up in the river channel. Afforestation reduces flood risk and water pollution | Dams, floodwalls and reservoirs are built to prevent flooding and ensure a regular supply of water |
| Floodplain zoning - restriction on building on certain areas of a floodplain | River straightening increases the flow of water by increasing the gradient of a river's channel and removing natural meanders (bends) |
| Riverbank conservation to reduce lateral bank erosion and collapse through planting to stabilise banks and reduce silting downstream |
Levees - natural ones can be increased in height to increase bankfull capacity Embankments can be built or increased using concrete or sustainable materials (usually dredged from channel) |
| River restoration aims to restore the river channel to its original course by removing and reversing past management strategies | Channelisation adds a liner to a straightened river channel (usually concrete) to reduce friction which aims to improve flow rate and therefore, reduce silting |
| Restoring natural wetlands on floodplains | Diversion spillways also called flood relief channels bypass the main river's channel during periods of high flood risk. They can also be a permanent feature which act as a wetland, and improve the local environment |
|
For - overall a cheaper method of management compared to hard engineering and can improve the local environment Against - planning restrictions limit building of new homes and businesses and difficult to implement in already urbanised areas |
For - prevents flooding of homes and businesses, thereby reducing costs of repairs and loss of revenue. Against - very expensive to build and maintain. They alter wildlife habitats and prevent aquatic migration. They affect river flow downstream - increased silting or flooding. |
