ABSTRACT
Roads cut across and obstruct natural drainage paths and, hence, there may be locations where flood waters have the power, if given the opportunity, to destroy a roadway by force or to hold up traffic by flooding a carriageway. The barrier effects of new roads can result in blockages on existing local drainage channels which cause redirection and redistribution of stream flows and alter local catchment areas and boundaries. Thus, good drainage design begins with good route location, and roads that avoid poorly-drained areas, unstable foundation soils, frequently flooded areas, and unnecessary stream crossings greatly reduce the costs and dangers associated with these aspects of road drainage. Good location may also make it more economic to relocate stream channels rather than provide bridges, major culverts and/or other expensive drainage features to accommodate them — assuming that the impacts of the proposed channel changes upon the environment are acceptable to the public.
