Overview of Urban Drainage Design
The objective of urban storm drainage is to optimize safe passage of vehicle traffic by collecting stormwater from the roadway, and to convey it safely to an adequate receiving body without undue risk to pedestrian traffic or contributing to damage of adjacent private properties during the design storm event.
The flow of water along a roadway can interfere with or halt highway traffic. The most destructive effects of an inadequate drainage system are damage to surrounding or adjacent properties, deterioration of the roadway components, and hazard or delay to traffic caused by excessive ponding in sags or excessive flow along roadway grades.
Proper drainage of a roadway in an urban region can be more difficult than draining roadways in sparsely settled rural areas for the following reasons:
- heavy traffic and subsequent higher risks
- wide roadway sections
- relatively flat grades, both in longitudinal and transverse directions
- shallow water courses
- absence of side ditches and a presence of concentrated flow
- the potential for costly property damages that may occur from ponding of water or from flow of water through built-up areas
- a roadway section that must carry traffic and act as a channel to carry the water to some disposal point.
These conditions require sound and consistent engineering principles and the use of all available data to achieve an acceptable drainage design.