What kinds of storms are roadside ditches and storm sewers currently designed and constructed for?
Under the City of Houston design guidelines, storm sewers and roadside ditches are designed for the 2-year frequency. The complete storm water system, including curb and gutter streets and/or roadside ditches acting as secondary storm water conveyors, is then checked with the 100-year storm event to verify that the water surface elevation is maintained within the public right-of-way. It is crucial to understand that Mother Nature will never produce rainfall events that replicate the parameters used in storm water engineering, since those events are the abstracted rainfalls based on the frequency distribution of historic rainfall records.
