Drainage management Flashcards
What do river regimes in an urban area point to?
The development of an urban hydrology
What is an urban hydrology characterised by?
- increase in total runoff
- increase in frequency of flooding
- decrease in lag time
- increase in peak discharge
4 types of hard engineering strategies?
- Diversion spillways
- Embankments
- River straightening
- River channelisation
What are diversion spillways?
Flood relief channels
Emergency use only, when high flow levels threaten flooding
Can create new wetlands and recreational opportunities
What are embankments?
Raised riverbanks, using concrete walls/material dredged from river bed -> more sustainable and environmentally friendly option
Increases capacity of river
What is river straightening?
Cutting through meanders to create a straight channel
Increases gradient and speed of flow
-> can increase flood risk further downstream
What is river channelisation?
Lining straightened channels with concrete
Reduces friction, improves rate of flow, reduces buildup of silt
-> can damage local ecosystems and looks unattractive
4 types of soft engineering strategies?
- Afforestation
- Riverbank conservation
- Floodplain zoning
- River restoration
How would afforestation affect drainage management?
Trees increase interception, reduce throughflow and surface runoff
Evapotranspiration dissipates water that would otherwise end up in river channel
What is riverbank conservation?
Planting bushes/trees reduces lateral erosion, bank collapse
Roots stabilise banks by binding loose material/sediment
What is floodplain zoning?
Restricts different land uses to certain locations on floodplain
Natural floodplains act as natural soak-away, reduces surface runoff
What is river restoration?
Return of channel to its natural course
What are SuDS?
Sustainable Drainage Systems: designed to efficiently manage drainage of surface water in urban environments
-> an alternative to traditional drainage systems
SuDS strategies?
- swales: wide shallow drainage channels, normally dry
- permeable road and pavement surfaces
- bioretention basins: gravel/sand filtration layers beneath reed beds/wetland habitats, collect, store and filter dirty water
Benefits of SuDS?
- slow down surface water runoff, reduce risk of flooding
- prevent water pollution
- provide habitats - increase biodiversity
- create recreational green spaces
- reduce demand on existing drainage systems
Example of SuDS scheme?
Lamb Drove, Camborne
Cost effective: construction + ongoing maintenance costs = 10% less than conventional pipe drainage systems -> however, cost implications in getting rid of old systems
Improvement in biodiversity and ecology
Open spaces + greener land = better mental health
