Urban Drainage Flashcards
(39 cards)
How do urban areas impact the water cycle? - Urban Drainage
Urban areas have increased precipitation due to the urban heat island effect/presence of condensation nuclei, increased runoff and reduced infiltration due to presence of impermeable surfaces, reduced evapotranspiration due to lack of green spaces, less throughflow and groundwater flow.
What is base flow? How is urban base flow different from rural base flow? - Urban Drainage
Base flow is the natural, residual volume of water that would be in a river had a flood NOT occurred. Urban base flow is lower than in rural areas due to reduced infiltration from impermeable surfaces.
How do urban areas impact the storage of water? - Urban Drainage
Urban rivers are significant stores of water, temporary stores such as puddles and surface water are significant, interception storage reduced as a result of a loss of vegetation (replaced by urban structures designed to rapidly drain water), soil moisture storage reduced as soil is often covered with impermeable surfaces.
How are precipitation levels affected by urban areas? - Urban Drainage
Precipitation levels are significantly increased as a result of the urban heat island effect, which generates warmer and more humid conditions, generating more frequent rain of greater intensity.
What is catchment management? - Urban Drainage
Catchment management is a way of managing rivers and improving drainage systems by observing a whole catchment, as well as interactions between water and land.
How are drainage systems valuable to cities and their populations? - Urban Drainage
Drainage systems provide important water resource management, sustain wildlife habitats, moderate urban climates, provide recreational areas/community facilities, regulate and monitor water quality.
What 2 methods are used to manage river catchments? Give examples of each - Urban Drainage
Hard engineering: dredging, flood defences, river channelisation (straightening/deepening of the channel), overflow channels, dams, levees, etc.
Soft engineering: electronic warning systems, afforestation, flood plain zoning (managing land use), sandbag use, river restoration schemes, managed retreat.
What urban issues do catchment management schemes aim to solve? - Urban Drainage
Catchment management schemes aim to avert urban issues such as flooding, drought, water pollution, erosion and ecosystem destruction.
What are typical features of hard and soft management strategies respectively? - Urban Drainage
Hard - typically man made structures, control natural processes, require planning, costly, unsustainable, may have long term benefits.
Soft - doesn’t change or manage the environment, instead working with natural processes, cheaper, sustainable, less intrusive.
Why was the LA Catchment Management Scheme introduced? What did this aim to produce? - Urban Drainage
The LA Catchment Management Scheme was introduced following flash floods in the 1930s, aiming to create a ‘fail safe’ strategy which could virtually never result in flooding.
What were features of the LA Catchment Management Strategy? - Urban Drainage
The LA Catchment Management Strategy saw the revived channel reconstructed from cement, an impermeable surface, in order to ensure that the flow of water was controlled and that excessive meandering could not be created.
What are advantages and disadvantages of the LA Catchment Management Scheme? - Urban Drainage
Advantages: heavily restricts possibility of any flooding, a highly regulated and managed river system.
Disadvantages: infrastructure may be vulnerable to earthquakes, destroying the management scheme. Has also seen the devastation of natural river habitats and ecosystems that previously existed here.
Who decides on catchment management measures? On what basis are changes introduced? - Urban Drainage
Catchment management measures are introduced by experts separate from an affected region rather than residents who will be impacted. These changes are brought in based on benefits for a catchment as a whole rather than individual residents, meaning some may face disruption.
What issues are involved with the management of drainage in urban areas? - Urban Drainage
Drainage management has to deal with water pollution, pesticide use (eutrophication), damage to wildlife, sewage management, balancing and regulation of water levels in the catchment to prevent flooding.
What are SUDS? What are their aims? - Urban Drainage
SUDS are systems which aim to imitate natural drainage systems in urban areas rather than channelling water through pipes and drains.
What do SUDS often result in? - Urban Drainage
SUDS frequently result in reduced flooding, less water pollution and less drought in urban areas. Can slow down runoff and allow natural processes to break down pollutants. Designed as being safe to fail.
How do rain garden planters achieve the aims of SUDS? - Urban Drainage
Rain garden planters filter water through soil rather than placing it directly into drainage, prolonging the process of drainage to reduce runoff and risk of flooding. Also filter any pollutants out of water and into soils.
How do water butts achieve the aims of SUDS? - Urban Drainage
Water butts help to achieve the aims of SUDS by storing water in a source for a prolonged period, meaning that runoff is regulated and therefore flooding prevented.
How do tree pits help to achieve the aims of SUDS? - Urban Drainage
Tree pits help to achieve the aims of SUDS as slanted impermeable surfaces can be used to divert excess runoff water towards plants and trees with roots that are able to absorb it.
How do swales help to achieve the aims of SUDS? - Urban Drainage
Swales create shallow channels with gently sloping sides, increasing the surface area of a permeable area and its capacity to hold water. This therefore means that infiltration is increased, runoff is managed and groundwater storage increased.
How does permeable paving assist SUDS in achieving their aims? - Urban Drainage
Permeable paving helps SUDS achieve their aims as small gaps in the paving allows water to infiltrate into the ground, reducing runoff and therefore preventing flooding. Also filters water through the paving, meaning that pollutants are extracted.
How do vegetated roofs help achieve the aims of SUDS? - Urban Drainage
Vegetated roofs are able to intercept rainfall and increase evapotranspiration, reducing flood risk.
What are the benefits of SUDS? - Urban Drainage
SUDS slow down runoff, prevent pollution of river systems, create green spaces, reduce flooding and work with natural environmental processes to manage drainage rather than creating expensive and intrusive drainage systems.
What is river restoration and conservation? What are its aims? - Urban Drainage
River restoration and conservation aims to restore river systems to a more natural state in order to reduce flood risk, decrease water pollution, create natural habitats and improve biodiversity.
