Recently the possibilities for creating wetlands in and around towns and cities have been given more attention, following the disappearance in recent decades of large stretches of wet nature, and thus also natural buffers, as a result of urban expansions and land drainage. Wetlands are created to buffer some of the run-off from precipitation and slow the rate at which it drains away. This is a new approach compared with rapid drainage systems using ditches and pipes. Another benefit of wetlands is that biological pollutants are eliminated by plant life and settle in the sediment, which significantly improves the quality of the run-off.