For many centuries, wet grasslands, river flood plains, salt marshes and other wetlands have been subject to alteration by man. Early navigation and the founding of ports and fortified settlements required drainage of marshy areas and the construction of access routes. The fertility of alluvial soils for cultivation has been long recognised, together with the value of wet grasslands for grazing. With the advent of tile and mole drains during the 18th Century, huge areas were drained for agricultural improvement. This was continued through the maximisation of agricultural production in the post war period. Flood control to allow industrial and urban development usually meant draining wetlands, channelling rivers and speeding the water on its way to the sea.
In recent years there have been many changes. The drive for maximum agricultural production is now past, and the emphasis on land drainage is gone. With water supply requirements becoming difficult to meet, changing weather patterns and lowering of water tables, the value of wetlands as huge ‘sponges’ has been realised. The emphasis is turning to retaining and absorbing water in inland wetlands, to replenish ground supplies, and slow the flow of water off the land. In coastal areas, water levels are expected to rise in the long term due to the greenhouse effect, with consequent flooding. Coastal areas which were previously ‘reclaimed’ from the sea are now seen as vital buffers against sea level rise and erosion, and are being returned to their natural state.
After years of being paid to drain land, landowners are now being paid to restore wet grassland. In the Somerset Levels, a £20 million pound flood defence programme is being implemented which includes payments to farmers to raise water levels in ditches to flood grassland. In many areas the technology and infrastructure of land drainage is being reversed and used to raise water levels and recreate wetlands.