Urban drainage and precipitation:

impact of urbanisation on permanent stores

these stores are vulnerable to evaporation

e.g. reservoirs, lakes

temporary stores: impacts of urbanisation

depression storage

e.g. puddles

interception storage:impacts of urbanisation

reduced as less vegetation, more impermeable surfaces

soil moisture storage: impacts of urbanisation:

varies depending on ground condition

clay retains more water than sand

urban river storage: impacts of urbanisation:

alters river flow, increase water in flow

Why are urban areas designed to shed water quickly?

the city does not want to store water on its roads/pavements, and water quality has become increasingly important, and groundwater is extremenly difficult to clean up.

Why is there reduced evapotranspiration in an urban water balance compared to a natural water balance

reduced vegetation and also reduced water stores

infiltration decreased due to more impermeable surfaces, so that is why in urban water balance, there are large volumes of poor quality runoff, unlike natural water balance with normal runoff due to more infiltration.

What are the 3 most important issues planners must consider when building urban areas:

very high flows can overload the foul water system resulting in raw sewage on the surface, which can lead to flooding but also the land being inhospitable due to it being so polluted → can harm biodiversity and allow diseases to run riot

increased flow leads to flooding, and erosion of river bank during wet periods

higher water temps can disturb ecosystems.

Impact of LA river drainage system:

environmentally, controlled river’s flooding, by directing it through a built channel, reducing its runoff, its ecosystem services having been removed.

socially and economically, the devestating flash flooding can be prevented, and its hard engineering, but if one part sustains damage, the entire system could be paralysed. moreover almost entirely concrete (lowk bad)