Urban streams are likely to face hydrological extremes (increased flow volumes during events and lower baseflow), stress on vegetation growth from adjacent land uses, and increased sediment and pollution loads.
If stream restoration projects fail, they may cause flooding and bank collapse, which consequently leads to sedimentation of downstream environments.
Urban stream restoration must therefore focus upon 'rehabilitation' as opposed to 'restoration', to ensure the sustainable recovery of stream processes in a form that responds to urban catchment conditions. This may not require hard structural measures, but may necessitate design consideration for stream profile, floodplains, and innovative methods to stabilise banks.
If stream corridors are part of a stormwater management response, they require protection and maintenance. The integration of stormwater management within a stream corridor might include:
- Treatment practices running in parallel with stream corridors such as filter strips, wetlands or infiltration trenches
- A widened buffer, back wetland, or alternative flow path to accommodate combined sewer overflows
- Allowing stormwater wetlands to be inundated by spring tide conditions to augment inanga spawning habitat
- Floodplain habitats.
WSD represents a significant opportunity to rehabilitate natural systems and processes in association with receiving environments. These systems can be an important contributor to regional biodiversity and for passage of fauna from coastal to upland environments.