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Rate of rainfall is expressed in.....
cm/hr
mm/hr
m/hr
km/hr
cm/hr
The rate of rainfall, often referred to as rainfall intensity, is defined as the depth of water accumulated over a specific surface area per unit time. In Indian engineering practice and hydrological standard reporting, this is typically expressed in centimeters per hour (cm/hr) or millimeters per hour (mm/hr).
The rate of rainfall, often referred to as rainfall intensity, is defined as the depth of water accumulated over a specific surface area per unit time. In Indian engineering practice and hydrological standard reporting, this is typically expressed in centimeters per hour (cm/hr) or millimeters per hour (mm/hr).
I=tDтАЛ тАФ where I is intensity, D is depth (cm/mm), and t is time (hr)
Rainfall intensity I is calculated as the ratio of the total depth of precipitation D measured by a rain gauge to the duration of the storm t. Mathematically, I=tDтАЛ. When standard units are used, depth is measured in linear units like cm or mm, and time in hours, resulting in units like cm/hr.
Rainfall intensity is a crucial parameter in the Rational Method for peak runoff estimation: Q=360CIAтАЛ.
In India, the India Meteorological Department (IMD) uses cm/hr or mm/hr for intensity observations.
Standard rain gauges measure the total depth over a fixed interval, allowing for the derivation of intensity.
Enables hydrological design of storm water drains.
Essential for calculating infiltration indices like ╬ж-index.
Point measurements may not represent spatial variation.
Intensity values vary significantly based on the chosen time duration.
Urban drainage system design
Flood forecasting
Design of hydraulic structures like bridges and culverts
While mm/hr is internationally common in scientific literature, cm/hr is traditional in many Indian civil engineering textbooks and state-level irrigation department reports.
Options B, C, and D represent linear measurements (depth/length) rather than a rate of occurrence over time.
A is correct тАФ The rate of rainfall is expressed as a depth per unit time, commonly represented as cm/hr in Indian engineering hydrology.
Always check the units in the denominator for 'rate' questions. If time is missing, it is simply 'depth', not 'rate'.
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