Primary Flooding Sources
The Big Sioux River and Skunk Creek are the two primary flooding sources affecting the City of Sioux Falls. The Big Sioux River upstream of Sioux Falls has a drainage area of 5,718 square miles. Skunk Creek is a tributary to the Big Sioux River and has a drainage basin of 570 square miles upstream of Sioux Falls.
What is a Flood?
Flood is defined in the Standard Flood Insurance Policy (SFIP), in part, as:
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A general and temporary condition of partial or complete inundation of two or more acres of normally dry land area or of two or more properties (at least one of which is your property) from overflow of inland or tidal waters, from unusual and rapid accumulation or runoff of surface waters from any source, or from mudflow.
Frequency of Flooding
Since 1881, the City of Sioux Falls has experienced flooding from the Big Sioux River 17 times and from Skunk Creek 7 times.
Cause and Time of Flooding
Most flooding events occur during the months of March and April and are caused by snow melt. Flooding caused by rain fall historically has occurred during the month of June.
Boundaries of Flood Hazard Areas
The areas subject to flooding are shown on the Flood Insurance Rate Maps (FIRM) dated September 1982 except in those areas identified below where the best available information is used for local floodplain management purposes. Flood Insurance Rate Maps (FIRM) are available for downloading from the link below or hardcopies are available from the Building Services Department.
Areas where the best available information available is used for local floodplain management purposes in place of the information contained on the FIRM maps for local floodplain management purposed. This information is more restrictive than the information shown on the FIRM maps.
- 41st Street Area of Shallow Flooding
The entire area bounded by Forty-First Street (South), Interstate 29 (West), Skunk Creek levee System (North), and the Big Sioux Levee System (East) has been included in the AO Zone.The highest adjacent grade for this area is established at 102.63 City datum or 1411.81 mean sea level. All structures must have their lowest floor elevation no lower than 104.63/City datum or 1413.81 mean sea level.
- Big Sioux River
The Base flood elevation on the Big Sioux River lying between Western Avenue and the Levee System located west on John Morrell and Company has been increased.For information on the base flood elevations in areas along this stretch of the Sioux River, contact the Sioux Falls Planning and Building Services Department (Zoning Division).
