Channelisation involves altering the natural geometry of a watercourse through hard engineering techniques. It is done to increase channel capacity and prevent flooding, provide straighter channels for navigation, prevent erosion, and reclaim wetlands. Specific channelisation methods include resectioning to widen and deepen channels, realignment to straighten meandering rivers, bank protection through structures, lined channels with concrete, containment within pipes and arches, vegetation clearance to remove obstructions, and dredging to remove sediment.