CUE - Urban Drainage Flashcards
hydrology of urban areas
lower evapotranspiration, high runoff, lower infiltration
more or less precipitation in urban areas?
more
ways in which urban areas move water quickly
sloping roofs
guttering (smooth and rounded)
camber of the road
storage areas in urban areas
reservoirs swimming pools rivers ponds/lakes (parks) puddles
urban storm hydrograph - lag time
lag time is short and surface runoff gets to the river quickly through the drainage system
urban storm hydrograph - rising limb
steep rising limb as surface runoff gets into the river quickly through drainage system
urban storm hydrograph - base flow
low base flow as low levels of ground/soil water due to impermeable surfaces
ways to increase the storage capacity of urban rivers
dredging
channelisation
what is hard engineering?
uses man made structures to prevent or control natural river processes from taking place.
what is soft engineering?
works alongside the natural processes to manage the risk
characteristics off hard management strategies (5)
require a lots of planning expensive changes or damages the environment unsustainable initial cost may save money in the long term
characteristics of soft management strategies (5)
doesn't change to damage the environment cheaper sustainable less intrusive can take a long time to be effective
hard engineering strategies is catchment management
diversion spillways
river straightening
river channelisation
natural levees and embankments
soft engineering strategies in catchment management
afforestation
riverbank conservation
river restoration
floodplain zoning
what does river straightening do?
they cut through meanders to create a straight channel, increasing the gradient and speed of flow, however may increase flood risk further downstream
describe diversion spillways
permanent feature, by passing the main channel, for emergency use
what is river channelisation?
lining straightened channels with concrete, reducing friction
what can be done to natural levees?
they can be made higher, increasing capacity
what are embankments?
raised riverbanks using concrete walls, blocks of stone or material dredged from the river bed
more sustainable option, looks more natural than concrete walling, more common in urban areas
what does afforestation do?
evapotranspiration dissipates water that would end up in the river channel
what does riverbank conservation do?
planting bushes and trees reduces lateral erosion, bank collapse and so silting up of the channel
what is river restoration?
return of the channel to its natural course and so the reversal o artificial drainage management ‘solutions’ in the past
what does floodplain zoning do?
restricts different land uses to certain locations
social benefits of lamb drove
improvement in quality of life
increases amenity and social value to residents and local community
economic costs of lamb drove
costs to build
economic benefits of lamb drove
construction and ongoing maintenance costs have been 10% les than conventional pipe systems
affordable houses
external funding
environmental costs of lamb drove
some people consider standing water to be a hazard (it isn’t)
environmental benefits of lamb drove
improvement in biodiversity and ecology
improved water quality (lower heavy metal concentrations)
reduces flooding
more attractive
location of lamb drove
Cambourne, west of Cambridge in Cambridgeshire
what is lamb drove?
a 35 affordable homes development
aims of lamb drove
to showcase practical and innovative sustainable water management techniques within new residential developments
to demonstrate that suds are a viable and attractive alternative to more traditional forms of drainage and to deliver practical solutions for new housing areas.
suds components in lamb drove
water butts permeable paving green sedum roof Swales detention basins and wetlands retention pond
what do water butts do?
collect roof water for garden irrigation
what does permeable paving do?
allows water to enter porous storage zones, and filter out pollutants
what does a green sedum roof do?
reduces and treats runoff
what do Swales do?
shallow open channels collect all excess water form the site, slowing the flow and continuing the treatment process.
what do detention basins and wetland do?
slow down runoff rage and store water on a temporary short-term basis during floods
what are retention ponds in lamb drove?
final storage of water before being released to a drainage ditch beyond the development site.
name of the river restoration case study
Cheonggyecheon river project
location of the Cheonggyecheon river
Seoul, South Korea
what was the water course of Cheonggyecheon originally like?
a small seasonal stream
why was Cheonggyecheon originally covered in?
it was seen as a sanitation and flood risk
2 aims of the Cheonggyecheon river project
improved connectivity between the north and south sides of the city
to create ecological and recreational opportunities in the centre of Seoul.
3 features of work done to restore Cheonggyecheon
the elevated freeway and concrete deck covering the stream were dismantled.
22 bridges built to improve movement from north to south.
water from the Hanang River is pumped in to create a consistent flow, which is treated to make sure it isn’t polluted
what did local businesses think about the Cheonggyecheon river project?
they originally saw it as an interruption or threat to their livelihoods
how many people now visit Cheonggyecheon?
millions (18.1 million by the end of 2008)
a piece of evidence to show that the Cheonggyecheon river project can be considered to be economically sustainable
since the restoration, development capital has been invested in residential construction and property prices have risen at double the rates elsewhere in the city
how has the Cheonggyecheon river project affected temperatures
2.5 C reduction in average temperatures in the area
why could the Cheonggyecheon river project be considered to be socially unsustainable
irregular surfaces are uncomfortable for people in wheelchairs and poorly lit, congested tunnels can be difficult for those with visual impairments and mobility issues
what problems might planners face in the UK if they shed to carry out a scheme such as Cheonggyecheon on a major British city
lengthy project
expensive - would need a lot of funding
would require planning permission and a lot of resources invested
stronger opposition from business and residents
traffic issues involving needing to reroute and careful consideration of existing routes
