How landscape change causes flooding in towns and cities

Flood protection

Upstream forest clearance and land drainage, combined with urban drainage from roofs and roads, is a major cause of flooding

‘In all the industrial countries, rivers have suffered from forest clearance in the uplands, farm drainage in the lowlands and water-proofing in urban areas. Forest clearance took place on the hills, in the valleys and on the plains. This accelerated water runoff. Ploughing and drainage took place in agricultural areas. This accelerated water runoff. River channels were deepened, widened, straightened and fixed. This accelerated water runoff. Large new urban areas were rendered partially impervious, with roofing and paving materials. This accelerated water runoff. The capacity of washlands and flood plains to accommodate peak volumes was diminished by building upon them. Accelerated water runoff raised flood peaks. It then became necessary to place urban rivers into underground culverts or concrete canals, or to supplement their capacity with ‘flood relief channels’. The net effect of all the changes was a dramatic increase in peak storm discharge. Embankments had to be built to prevent overtopping by floodwater. When these works are viewed together it is clear that they do not constitute a good use of public or private expenditure.’ (Tom Turner Landscape planning and environmental impact design 2nd edition 1998 p.294)

SUDS Sustainable Urban Drainage Systems

The susainable landscape approach to flood protection relies on water detention, infiltration and evapo-transpiration.

Landscape architects can offer an ecological and economical solution to the flooding problem in villages, towns, cities and other urban areas: water should be detained, infiltrated and Collectively, these policies can be described as Urban Surface Water Management, Sustainable Urban Drainage Systems and Water Sensitive Urban and Landscape Design.

Tom Turner

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