Resilience measure: Conventional urban drainage systems

definition

The purpose of urban drainage systems (a.k.a. collection systems) is to enable safe and reliable disposal of stormwater runoff (i.e., they are at the first place used for pluvial flood protection) and removal of wastewater from urban areas. These systems can be either combined, separate or hybrid. They can be in the form of open channels or closed conduits. The term ‘sewers’ usually refers to the network of closed conduits (i.e., piped systems) which are used to convey the flow from a certain area, whereas the term ‘sewerage’ refers to the entire wastewater/stormwater system infrastructure in the particular city. The key elements of urban drainage systems are: reticulation or collection networks (pipes, rising mains, channels, culverts, manholes, etc.), gully inlets (a.k.a., catchpits), ventilation shafts, chambers and tanks, combined sewer overflows and sanitary sewer overflows, outfalls, controls (orifices, gates, penstocks, vortex regulators, flap valves, etc.), pumping stations, bifurcations, weirs, inverted siphons, treatment and other ancillary structures, storages (offline, online, open, closed, above-ground, below-ground, retention and detention ponds), watercourses, boverland flow paths and designated floodplains, dams, multipurpose tunnels and so on (Vojinovic Z., 2015, p. 97).

Co-benefits and impacts

Apart from preventing water accumulation, drainage systems have also the advantages to reduce soil erosion and remove toxic materials and disease organisms by draining the contaminated water away. However, urban litter can be a major problem for the functioning of urban drainange systems. Once it enters the drainage system, the litter is potentially able to travel via the stormwater pipes or channel, either until it eventually reaches the receiving water or creates an obstruction and creates blockages along the way. (Vojinovic Z., 2015, p. 97)
However, permitting stormwater into sewers or combined sewers can lead to higher pumping requirements and the increased risk of sewer overflows. Moreover, efficiently conveying flow away from catchments can increase the serverity of flooding downstream.

conditions

Conventional drainage can beapplied in urban and rural settings. They can also serve as a backup conveyance mechanism for "water sensitive urban design" stormwater elements. The impacts of their construction on the risk of downstream fooding should be considered prior to their adoption.

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Last modified: Jan. 18, 2017, 12:17 p.m.