Leats are waterways designed to feed other waterways, or to supply water-powered mills and industries. They are usually fairly narrow, but in urban areas may be as big as canals and serve as much to transport goods as to supply water. Smaller leats feed off-stream ponds where they often lead by a gradual route along the contours. Examples are found on many large estates such as Fyne Court, Somerset, but the inflow to any suspected man- made pond is worth investigating for tell-tale straight lines, paved bottom and steep banks under the moss, overhanging shrubs and accumulated leaves and silt. Villages often diverted water from nearby streams past houses and industries, as at Sticklepath, Devon, where the leat is tapped for the wheel-run trip hammers, shears and blowers of the old forge, now a museum. Such courses are usually equipped with sluices to control levels and divert the flow as required.
Ditches, including drains and dykes of all sizes, are as numerous as natural channels in most parts of the country. They were dug primarily to drain the land and act as boundaries, but may also have served for irrigation, flood control and navigation purposes. Simple grip and cut-off drains were in use in pre-Roman times to keep homesteads dry and field plots workable. The Romans started large-scale drainage works in Romney Marsh and the East Anglian Fens. The great age of open drains was during the 17th Century, when the Somerset Levels, East Anglian Fens and the Don Valley were drained for agriculture. Drainage causes oxidation and settlement of the fen peat which results in the fens shrinking lower than the surrounding land, and water must be continually pumped out to prevent flooding.
Interesting features of today’s fenland are the extinct river channels or ‘roddings’ left winding across country above the level of the skirtland to either side. The roddings form stable platforms and often have houses or roads built along them.
By the early 18th Century hollow tile drains became available, and the technique of making mole drains in clay soil was developed. This involves the pulling of a special plug-shaped plough through the soil to form an unsupported under-drain. The middle years of the 19th Century saw the massive spread of these techniques to improve land for agricultural production, and since then have followed cycles of dereliction and renewal according to the changes in the agricultural economy.