Urban Stormwater

Ohio Stormwater Control Guidebook

Stream Channel and Flood Plain Erosion

To control pollution of public waters by soil sediment from accelerated stream channel erosion and to control flood plain erosion caused by accelerated stormwater runoff from development areas, the increased peak rates and volumes of runoff shall be controlled such that:

1. The peak rate of runoff from the critical storm and all more frequent storms occurring
   on the development area does not exceed the peak rate of runoff from a one year
   frequency storm (of 24 hours duration) occurring on the same area under predevelopment
   conditions.
2. Storms of less frequent occurrence than the critical storm, up to the one hundred
   year storm, have peak runoff rates no greater than the peak runoff rates from
   equivalent size storms under pre-development conditions.

The critical storm for a specific development area is determined as follows:

1. Determine by appropriate hydrologic methods the total volume of runoff from a oneyear
   frequency, 24-hour storm occuring on the development area before and after
   development.
2. From the volumes determined in (a), determine the percentage increase in volume of
   runoff due to development, and using this percentage, select the 24-hour critical
   storm from this table.

For questions or additional information, please contact:

John Mathews
Urban Stormwater Specialist
614-265-6685