South Carolina Unit Hydrograph Method Applications Manual & Application Excel Workbook
This manual covers the development and application of the South Carolina Unit Hydrograph (SC UH) Method. Topics included are unit hydrograph Peak Rate Factors based on land use in the watershed, curve number modification for rainfall durations less than 24 hours, time of concentration, NOAA Rainfall Distributions, and critical rainfall duration.
The Excel workbook allows the user to apply the SC UH Method, determine the critical rainfall duration for flow and volume, design ponds, export hydrographs to other applications, and determine sediment trap efficiency.
Rainfall Intensity Values
The Rainfall Intensity Values are based on NOAA Atlas 14 Point Frequency Estimates for each county’s centroid. These intensity values were used to develop Intensity – Duration – Frequency (IDF) curves with the help of the FHWA’s Hydraulic Toolbox software. The coefficients for the IDF equation and Rainfall Intensity Values for given durations and frequencies are shown in the tables by county.
SCDHEC Approved Rainfall Data
SCDHEC has promulgated two ways of determining the 24 Hour Storm Event for South Carolina. One is in Appendix F of the 2005 BMP Handbook. This appendix is attached in the pdf document below. The other method is using NOAAs Hydrometeorological Design Studies Center. This method requires the Longitude and Latitude of the project. Both of these methods are acceptable to SCDHEC.
Department of Natural Resources
The Department of Natural Resources provides access to topographic, land use, and aerial maps that can be downloaded as well as information about the digital elevation and world coordinates data.
Natural Resources Conservation Service
The Natural Resources Conservation Service provides information you can download such as Technical Release 55, Windows Technical Release 55, Technical Release 20, and Windows Technical Release 20. Also, this site has a reference to obtain county soil surveys.
Roadway Design Manual
The Roadway Design Manual assists technicians and engineers in selecting the needed design criteria in preparing plans for SCDOT construction projects.