# How do you calculate rainfall intensity of rainfall data?

## How do you calculate rainfall intensity of rainfall data?

Formula Of Rainfall Intensity The intensity of rainfall (p) in mm/hr is given by the following general formula: p = 254a / (t+b) mm/hr Where, t = Duration of storm in minutes, a and b are constants. a = 30 and b = 10 when t is 5 to 20 minutes. a = 40 and b = 20 when t is 20 to 100 minutes.

## What is design rainfall intensity?

The design rainfall intensity is the intensity of a constant intensity design storm having the specified design return period and duration equal to the time of concentration for the drainage area.

How do you calculate rainfall depth and intensity?

Rainfall intensity is often Rainfall Depth over a particular time. You need to accumulate the rainfall data for the the time step you are interested and then divide by that time. If you have rainfall intensity already, just multiply by the time step to get the depth.

How do you calculate rainfall data?

Add together all of the monthly rainfall totals in your sample data. You’ll be adding measurements in inches because rainfall is generally measured in inches in the United States. Divide by the number of years in your data set to arrive at the average monthly rainfall for any location.

### How is design rainfall intensity calculated?

Then the design rainfall intensity is calculated with the equation i = a/( d + b ) using the calculated values for a and b. Finally the design peak storm water runoff rate is calculated using the Rational Method equation, Q = CiA.

### What does 10 mm rainfall mean?

Very heavy rain: Greater than 8 mm per hour. Slight shower: Less than 2 mm per hour. Moderate shower: Greater than 2 mm, but less than 10 mm per hour. Heavy shower: Greater than 10 mm per hour, but less than 50 mm per hour.

How are rainfall intensity and duration and storm frequency related?

Intensity–Duration–Frequency (IDF) relationship, or IDF curves, is a representation of intense rainfall events that allows for calculation of a peak flow needed to design hydraulic structures (e.g., storm sewers, culverts, drainage systems), to assess and predict flood hazard, and design flood protection structures [1– …

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 rainfall intensity from time of concentration?

Equation 4.1 Q = I *A *0.00278 Where Q = peak discharge (m3/s) I = rainfall intensity (mm/hr) A = area (ha). of concentration and ARI. Equation 4.1 can be applied to any ‘catchment’ if it is assumed that all of the rainfall resulted in runoff.

## Is 10 20mm rain a lot?

Slight rain: Less than 0.5 mm per hour. Moderate rain: Greater than 0.5 mm per hour, but less than 4.0 mm per hour. Moderate shower: Greater than 2 mm, but less than 10 mm per hour. Heavy shower: Greater than 10 mm per hour, but less than 50 mm per hour.

What does 100 mm rainfall mean?

One millimeter of rainfall is the equivalent of one liter of water per square meter. The standard way of measuring rainfall or snowfall is the standard rain gauge, which can be found in 100-mm (4-in) plastic and 200-mm (8-in) metal varieties.

What’s rainfall intensity?

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 It is expressed in depth units per unit time, usually as mm per hour (mm/h).

### How do you calculate rainfall intensity?

In summary, rainfall intensity is calculated by dividing the amount of rain accumulated by the period of time during which this happens. Rainfall intensity is to rainfall amount what speed is to the distance traveled in a mechanical analogue.

### How do you calculate rain?

Calculate how much rainfall is in your container. For circular containers, for example, divide the diameter of the container by 2 to find the radius. Multiply the radius by itself, multiply that number by the number of inches of rain in the container and multiply that by 3.14 to find the total number of cubic inches of rain in your container.

What is the frequency of rainfall?

rainfall frequency (Also called frequency curve.) The probability distribution specifying the exceedance probability of different rainfall depths for a given duration (such as 1 hour, or a 24-hour day).

What is precipitation intensity?

precipitation intensity. [prə‚sip·ə′tā·shən in‚ten·səd·ē] (meteorology) The rate of precipitation, expressed in inches or millimeters per hour. Also known as rainfall intensity.