Low-lying and poorly drained land often requires surface drainage to drain excess water. Surface drainage is widely used by farmers in the Red River Valley of the North American Great Plains. The land of this expansive valley is nearly level and the soil has very poor internal drainage. It contains an intensive, municipal drainage network. Additional, in-field surface drains are constructed by farmers using earth scrapers. These surface drains are shallow and follow the natural drainage of the land. Because these drains are tilled as part of the field, they fill in with soil and require regular cleaning. The soil removed from these drains is normally spread on the adjacent land.
An extreme example of surface drainage is the dyked lands surrounding the Bay of Fundy in Atlantic Canada. Land is reclaimed from the sea using large dykes and drainage systems. A dense system of small shallow ditches (runs) conveys water away to larger ditches which convey water to outlets at the dyke. The land between the ditches (dales) is shaped or crowned using large blades. The moldboard plow is used to maintain the crown. This is done by placing the back furrow in between the ditches along the crown and placing the dead furrows along the ditches. Soil is progressively moved toward the crown between the ditches. It is necessary to continue to plow in this fashion to counter the leveling effect of other tillage operations.
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