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The Number of Days after Peak refers to the number of days after the peak is achieved in hydrograph analysis. This calculation helps in understanding the recession limb of a hydrograph and predicting the time required for the flow to return to normal levels after a peak event.
The calculator uses the formula:
Where:
Explanation: The formula provides an empirical relationship between catchment area and the number of days required after the peak flow is achieved.
Details: Accurate estimation of the number of days after peak is crucial for flood forecasting, water resource management, and designing hydraulic structures. It helps in predicting the duration of high flow conditions and planning appropriate mitigation measures.
Tips: Enter the catchment area for hydrograph analysis in square kilometers. The value must be valid (area > 0).
Q1: What is the significance of the 0.84 coefficient?
A: The coefficient 0.84 is an empirical constant derived from regression analysis of hydrological data, representing the relationship between catchment area and recession time.
Q2: Why is the exponent 0.2 used in the formula?
A: The exponent 0.2 indicates that the number of days increases with catchment area, but at a decreasing rate, reflecting the non-linear relationship between area and recession time.
Q3: Can this formula be applied to all types of catchments?
A: While the formula provides a general estimation, it may need adjustment for catchments with unusual characteristics such as steep slopes, urban areas, or significant groundwater contributions.
Q4: How accurate is this empirical formula?
A: The formula provides a reasonable estimate for preliminary analysis but should be validated with local hydrological data for critical applications.
Q5: What are the limitations of this calculation?
A: The formula does not account for factors like rainfall intensity, soil moisture conditions, land use changes, or climate variations that can affect the recession limb of a hydrograph.