Short-term Runoff Tools
SedSpec is an expert system that will assist you in analyzing runoff and erosion problems on your site by determining the peak rate of runoff from the area. The analysis will provide information about different types of runoff and erosion control structures.
The Rational Method is a simple method of predicting the peak rate of runoff. It is an oversimplification of the complicated runoff process, but it is considered accurate enough for runoff estimation in the design of relatively inexpensive structures where the consequences of failure are limited (i.e, failure will not result in loss of life). This tool returns the peak rate of runoff, the depth of runoff (computed using the SCS CN method), the computed time of concentration (using the Kirplich formula), and the corresponding rainfall depth.
- Technical Release 55 (TR-55) presents simplified procedures for estimating runoff and peak discharges in small watersheds. While this TR gives special emphasis to urban and urbanizing watersheds, the procedures apply to any small watershed in which certain limitations are met. This tool will return the peak rate of runoff, the depth of runoff (computed using the SCS CN method).
- Precipitation Database. Here you can retrieve rainfall depths from the databases used by SedSpec. You can choose between Technical Paper 40 (TP-40), Midwestern Climate Center (only has data for Illinois, Indiana, Iowa, Kentucky, Michigan, Missouri, Ohio, and Wisconsin), and North Carolina Erosion and Sediment Control Planning and Design Manual. You download a text (CSV ) file of daily averages for 30 to 32 years.