Flood

Water catchment systems, and water flow patterns can be protected and modified to improve flood prevention; for example, banning upland clear-felling and deforestation, ensures that water does not simply rush down the hills into the valleys and settlements below, washing away soil and houses. Through the application of on-contour swales and afforestation to retain water in upslope and agricultural areas the velocity and volume of water entering the system down-slope is restricted, reduced, moderated and more gradual, at the same time as increasing production of timber and tree crops for fodder, fuel, housing and food.

The creation of dams, self-closing flood barriers, river and coastal defences, and temporary perimeter barriers are generally more recognised forms of flood defence systems. Flood ponds receive peak volumes of water during inundation, and are increasingly employed in and around towns and cities, in addition to a network of channels, canals, trenches and ditches to collect, drain and divert water away from crucial areas such as population centres, back into natural fluvial networks, seas and oceans.

Individual buildings can be made more resilent by adding flood barriers to the doors, building them above groundlevel ie building on raised platforms and stilts, or creating deep reinforced foundations to reduce the likelihood of the structure being swept away. In areas particularly suceptible to regular flooding some buildings, sections of roads and barriers, have been designed specifically to float in the event of a flood.