The Rainfall Intensity is defined as the ratio of the total amount of rain (rainfall depth) falling during a given period to the duration of the period is calculated using Intensity of Precipitation = (Coefficient k for area represented by the station*Return Period^Coefficient x in the Equation)/(Time of Concentration+ …

How do you calculate rainfall intensity from rainfall depth?

The first thing that you have to do is to convert the table of annual maximum (statistical) values of rainfall depth into Intensity Values (mm/hr) just divide the total depth (precipitation) by the rainfall duration (i.e. for 1971 during 1 hr you have a rainfall max.

How do you calculate rainfall intensity in Excel?





The Excel formulas in the spreadsheet are set up to calculate the constants, a and b, in the equation i = a/( d + b ), by linear regression of 1/i vs d. Then the design rainfall intensity is calculated with the equation i = a/( d + b ) using the calculated values for a and b.

How do you calculate rainfall intensity in rational method?

The Rational method predicts the peak runoff according to the formula: Q=CiA, where C is a runoff coefficient, i is the rainfall intensity, and A is the subcatchment area. This formula is applicable to US or metric evaluation, as long as consistent units are employed.

What is rainfall intensity and duration?

The rainfall intensity–duration–frequency (IDF) curves are graphical representations of the probability that a given average rainfall intensity will occur within a given period of time (Dupont and Allen 2000).

What is rainfall intensity?

Rainfall intensity is determined as the average rainfall rate in mm/h or mm/min for specific rainfall duration and a selected frequency. In many regions, data on rainfall intensity are available with a sufficient spatial and temporal resolution. Often these data are given as rainfall height for a defined duration.

How do you calculate rainfall intensity from annual rainfall data?





It is calculated by dividing the depth by the duration and is simply a measure of the ‘heaviness’ of the rainfall.

How do you calculate the rainfall intensity from the IDF curve?

A similar exercise can be done for T1 = 20min and T2 = 60min. Once this is done, the equation we will have two equations relating time to precipitation for the specific MSP. Then, I = P/T*60 can be used to determine the rainfall intensity “I” for any time of concentration “T” between 5 and 60 minutes.

What is Horton’s equation?

The original Horton equation was given as follows. (1) f ( t ) = f c + ( f 0 – f c ) e – k t where f0 is the initial value of infiltration capacity (mm/h) at the beginning of rainfall; k is the soil-specific decay constant.

How do you calculate rainfall per hour?

Quote from the video:
Quote from Youtube video: Intensities is usually expressed in centimeter per hour these are the general units of 24 intensities mainly in centimeter per hour or millimeter per hour if the rainfall depth is in centimeter.

How do you calculate rainfall deviation?



Meteorologists do this by computing the Coefficient of Variation. The Coefficient Variation is simply the standard deviation divided by the average annual rainfall. For San Francisco’s average rainfall of 21.79″ for its period of record, the standard deviation is 7.63″. Dividing 7.63 by 21.79 gives 0.35.

How do you calculate time intensity frequency?

(1) P T = P ave + K S where K is Gumbel frequency factor given by:(2) K = – 6 π 0.5772 + ln ln T T – 1 where Pave is the average of the maximum precipitation corresponding to a specific duration.

What is frequency intensity and duration?

Frequency, duration and intensity are quantitative dimensions which describe the amount of physical activity taking place during a given time-frame (e.g. one week, one month, one year).

What is time of concentration used for?



Time of concentration is a concept used in hydrology to measure the response of a watershed to a rain event. It is defined as the time needed for water to flow from the most remote point in a watershed to the watershed outlet. It is a function of the topography, geology, and land use within the watershed.

How do you calculate time of stormwater concentration?

When the drainage area consists of several different types of surfaces, time of concentration is calculated by adding the time for each type of flow along the flow path from the watershed divide to the watershed outlet. Time of concentration is generally applied only to surface runoff.

What is the TR 55 method?

Technical Release 55 (TR-55) presents simplified procedures to calculate storm runoff volume, peak rate of discharge, hydrographs, and storage volumes required for floodwater reservoirs. These procedures are applicable in small watersheds, especially urbanizing watersheds, in the United States.

How do you calculate sheet flow?

Sheet flow generally occurs in the headwater of streams. The following equation is used to describe sheet flow: T t = 0.007 ( n L ) 0.8 ( P 2 ) 0.5 s 0.4 {\displaystyle T_{t}={\frac {0.007(nL)^{0.8}}{(P_{2})^{0.5}s^{0.4}}}}

How do you calculate stormwater flow?



Therefore, to assure that the first flush is captured and treated, the easiest method to determine the stormwater treatment volume is simply to multiply the project size or contributing drainage area times the treatment volume.

How do you calculate flow length?

This distance is measured along the direction of flow, not “as the crow flies”. Definition (GIS): In GIS, the flow length of an arbitrary pixel is determined by summing the incremental distances from center-to-center of each pixel along the flow path from the selected pixel to the outlet pixel.