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Unit of intensity of rain fall is....
mm/h
lit/min
lit/day
none of these
mm/h
Intensity of rainfall is defined as the rate at which rain falls, expressed as the depth of water per unit time. The standard SI-derived unit used in hydrology is millimeters per hour (mm/h).
Intensity of rainfall is defined as the rate at which rain falls, expressed as the depth of water per unit time. The standard SI-derived unit used in hydrology is millimeters per hour (mm/h).
i=tPтАЛ тАФ where i is intensity, P is precipitation depth, and t is duration
Rainfall intensity (i) is calculated by dividing the total depth of precipitation accumulated over a specific catchment area (P) by the duration of the storm (t). Mathematically, it represents the derivative of accumulated rainfall with respect to time (i=dtdPтАЛ). It is a critical parameter in the Rational Method for estimating peak runoff in urban drainage and watershed design.
Rainfall intensity is a scalar measure of precipitation rate.
Used extensively in the Rational Formula: Q=3601тАЛCIA.
Measured using self-recording rain gauges (tipping bucket or float type).
Units commonly used include mm/h, cm/h, or inches/h.
Simplifies calculation of runoff volume in small catchments.
Essential for designing hydraulic structures like culverts and storm drains.
Does not account for spatial variation over large areas.
Averaging over time can hide peak short-duration bursts.
Urban drainage system design.
Flood forecasting and warning systems.
Soil erosion studies.
The intensity is often represented on an Intensity-Duration-Frequency (IDF) curve.
Options B (lit/min) and C (lit/day) represent discharge (volume per time), not intensity (depth per time), making them dimensionally inconsistent for intensity measurement.
A is correct тАФ The unit of intensity of rainfall is defined as depth per unit time, specifically mm/h.
Always distinguish between 'Intensity' (Depth/Time) and 'Discharge' (Volume/Time). Intensity is depth-based, whereas discharge depends on the catchment area.