the 1762 act created the witham navigation commissioners and the witham drainage general commissioners, who continued to promote drainage schemes actively, creating a drainage network known as the witham navigable drains that transformed much of northern lincolnshire from fen to farming land. today many of these channels are managed by the witham first, third and fourth district internal drainage boards and upper witham internal drainage board. these four internal drainage boards reduce the flood risk to the surrounding properties, land and environment.