swales

noun

1. 1.A low tract of moist or marshy land.
2. 2.A long narrow and shallow trough between ridges on a beach, running parallel to the coastline.
3. 3.A shallow troughlike depression that's created to carry water during rainstorms or snow melts; a drainage ditch.
4. 4.A shallow, usually grassy depression sloping downward from a plains upland meadow or level vegetated ridgetop.
5. 5.A shallow trough dug into the land on contour (horizontally with no slope), whose purpose is to allow water time to percolate into the soil.