#Kinematic equation calculator how to
#Kinematic equation calculator manual

Watershed Time of Concentration Calculations with the NRCS Method units at a very low cost in our spreadsheet store. This Excel spreadsheet and others for time of concentration calculations are available in either U.S.

A tables with values of the Manning roughness coefficient for various overland flow conditions is also given below. units using the Manning kinematic equation, based on the input values entered for the other parameters listed above. The screenshot of an Excel spreadsheet template shown below will calculate overland sheet flow travel time with U.S.

P = 2 year, 24 hr rainfall depth, in (S.I.

n = Manning roughness coefficient, dimensionless*.

The equations in the boxes both give travel time in minutes.)

t 1 = overland sheet flow runoff travel time, min (NOTE: many places show the constant being 0.007 for U.S.

The parameters in the Manning Kinematic equation and their units are as follows: The boxes at the right show the Manning Kinematic equation for U.S. Typically overland sheet flow will occur in the upper portion of the watershed, followed by shallow concentrated flow, with channel flow for the final portion of watershed before the outlet.Ĭalculations with the Manning Kinematic Equation

#Kinematic equation calculator manual

The Iowa Stormwater Management Manual (ref #2) also recommends these three methods. Soil Conservation Service (SCS) in ref #1 at the end of this article. These three methods are recommended by the U.S. The following three equations will be discussed in this article: 1) the Manning Kinematic equation for use with overland sheet flow, 2) the NRCS method for shallow concentrated flow, and 3) the Manning equation for channel flow.

Some examples are the Kerby equation, the Izzard equation, the Manning Kinematic equation, the Bransby Williams equation, the National Resources Conservation Service (NCRS) method, and the Manning equation. There are several empirical equations that have been developed for calculating travel time/time of concentration for different types and conditions of watersheds. Methods for Estimating Watershed Time of Concentration

#Kinematic equation calculator how to

We can now move on to a discussion of how to calculate values for the time of concentration of a given watershed. Thus the maximum peak storm water runoff rate for a specified return period on a given watershed will be for a storm with duration equal to the time of concentration of that watershed. If the storm duration is greater than the time of concentration, then the storm will continue longer than it takes for the entire watershed to contribute to the outflow, but the storm intensity will be less for a storm of longer duration than one of short duration for a given return period. Thus flow from the entire watershed will never all be contributing to the outflow. This can be reasoned out as follows: If the storm duration is less than the time of concentration, then the storm will end before runoff from the entire watershed reaches the outlet. The reason that the watershed time of concentration is used as design storm duration is because it gives the largest peak storm water runoff rate for a given return period. The main reason for interest in the watershed time of concentration is for its use as the storm duration in finding the design rainfall intensity to use in Rational Method calculation of peak storm water runoff rate. The time of concentration for a watershed is the time for rainfall that lands on the farthest point of the watershed to reach the outlet. Read on for information about Excel spreadsheets that can be used for watershed time of concentration calculations. Obtain a convenient, easy to use spreadsheet for watershed time of concentration calculation at a reasonable price. To obtain an Excel spreadsheet for watershed time of concentration calculations, click here to visit our spreadsheet store. Where to find Excel Spreadsheets for Watershed Time of Concentration