AS 19.10.230: Method of construction of highway ditches.

A highway constructed or reconstructed shall be designed to permit water to drain from it into ditches which shall drain into coulees, rivers, and lakes according to the surface and terrain where the highway is constructed in accordance with scientific highway construction and engineering in order to prevent the water from overflowing onto adjacent and adjoining land. The natural flow and drainage of surface water may not be obstructed, but it shall be permitted to follow the natural course according to the surface and terrain.