What is SCS unit hydrograph method?
The SCS (Soil Conservation Service) unit routing model uses a curvilinear unit hydrograph to calculate runoff resulting from subcatchment net rainfall. The SCS method uses a dimensionless unit hydrograph derived from the analysis of extensive measured data.
What is SCS model?
Basic Concepts and Equations. The Soil Conservation Service (SCS) Curve Number (CN) model estimates precipitation excess as a function of cumulative precipitation, soil cover, land use, and antecedent moisture, using the following equation: Pe=(P−Ia)2(P−Ia)+S.
What is SCS CN model?
The Soil Conservation Service (SCS) curve number (CN) model developed by the U.S. Department of Agriculture National Resources Conversion Service (NRCS) is the most popular and widely applied model for direct runoff estimation.
Why are unit hydrographs useful?
A unit hydrograph shows the temporal change in flow, or discharge, per unit of runoff. In other words, how the flow of a stream will be affected over time by the addition of one unit of runoff. The unit hydrograph is a useful tool in the process of predicting the impact of precipitation on streamflow.
What is a 2 hour unit hydrograph?
We divided each hydrograph ordinate by two, resulting in a 2–hour Unit Hydrograph, i.e. One inch of direct runoff total from the 2 hour storm make a 1 hour UH. Tb is the time base. Define “ordinate”
What are the limitations of unit hydrograph?
LIMITATIONS OF A UNIT HYDROGRAPH: i)Unit hydrograph method is not applicable to areas with a major portion of storm precipitation being on form of snow. ii)Principle of time in-variance sometimes does not hold as the basin characteristics will chabge with man made adjustments as well as seasons.
What are hydrographs used for?
In its simplest form, a hydrograph is a graphical representation of runoff rate against time (Figure 1). It shows the time distribution of runoff at the point of measurement or computation, reflecting the complex characteristics of the watershed by a single curve.