Swamps were historically often drained to provide additional land for agriculture, and to reduce the threat of diseases born by swamp insects and similar animals. Swamps were generally seen as useless and even dangerous. This practice of swamp draining is nowadays seen as a destruction of a very valuable ecological habitat type of which large tracts have already disappeared in many countries.
A coastal swamp is always flooded whenever the tide rises. Similarly, swamps that are found inland become waterlogged whenever nearby rivers overflow their banks during the wet seasons. The role of wetlands and swamps is not limited to the retention of water. Wetlands act like natural sponges as they capture surface runoff water and bring it back to the surface slowly, preventingseriou water level control problems. They also limit soil erosion. The plants take root in them and absorb the effects of the wind and slow the current along the shore as well as sudden water level changes.
Dykes are built along the coast to keep the sea water out of the former swamps. Freshwater is brought in from a river through a network of canals. Excess water in the reclaimed land us removed by a system of drains. In this way, more land is made available for farmland. One example of land reclamation through draining swamps is the Tanjong Karang Land Reclamation Scheme in Selangor, Malaysia.
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