Flood Discharge Calculator for Empirical Methods Used in India
This calculator implements several empirical formulas for estimating peak flood discharge (Q in m³/s) based on catchment area (A in km²). These methods are commonly used in various regions of India for hydrological designs such as bridges, dams, and spillways. Constants (C) are region-specific and can be adjusted based on local conditions like rainfall intensity.
Input Parameters
Comparative Chart of Empirical Methods
| Method | Equation (Q in m³/s, A in km²) | Typical C Values | Applicable Locations/Regions | Conditions/Remarks |
|---|---|---|---|---|
| Dickens Formula | Q = C × A^(3/4) | 11.4 (annual rainfall 60-120 cm), 14-19.5 (MP, Maharashtra), 22 (Northern India with heavy rainfall) | North and Central India (e.g., Madhya Pradesh, Uttar Pradesh, Bihar) | Applicable for moderate to large catchments with higher rainfall intensity. Empirical, based on area only; does not account for rainfall duration or return period. Use with caution for very small or very large areas. |
| Ryves Formula | Q = C × A^(2/3) | 6.75 (within 80 km from east coast), 8.45 (80-160 km from coast), 10.1 (limited hilly areas), up to 30 for heavy rainfall zones | Southern India (e.g., Tamil Nadu, Karnataka, Andhra Pradesh) | Suitable for moderate rainfall intensity areas. Primarily for catchments in peninsular India; empirical and area-based. Not ideal for extreme events or non-homogeneous catchments. |
| Inglis Formula | Q = (124 × A) / √(A + 10.4) | N/A (fixed constants) | Western India (old Bombay Presidency: Maharashtra, Gujarat, parts of Karnataka; especially fan-shaped catchments in Western Ghats) | Developed for regions with variable topography like ghats. Accounts for area saturation effects; better for larger catchments. Not applicable to Deccan plateau or eastern regions. |
| Nawab Jung Bahadur Formula (Ali Nawaz Jung Bahadur) | Q = C × A^(0.993 - (1/14) × log10(A)) | 48-60 (Southern parts), up to 83.5-118 for other areas | Deccan Plateau (old Hyderabad State: Telangana, parts of Andhra Pradesh, Maharashtra) | Adjusts exponent based on area size for better accuracy in varying scales. Empirical; suitable for semi-arid to moderate rainfall regions. Higher C for northern variants. |
| Fuller's Formula | Q = C × A^0.8 × (1 + 0.8 × log10(T)) × (1 + 2.67 / A^0.3) (T: return period in years) | C ≈ 0.18-0.4 (adjusted for units; often in FPS, convert accordingly) | Various parts of India, but less region-specific; used where return period data is available | Includes return period (T), making it more versatile for probabilistic estimates. Originally in FPS units; ensure metric conversion. Suitable for gauged catchments; empirical correction for small areas. |
| Myers Formula | Q ≈ 123 × √A (approximate metric equivalent for maximum flood) | N/A (fixed for max flood) | General use in India for estimating absolute maximum possible flood | Conservative estimate for worst-case scenarios. Original in FPS (Q = 10000 √M, M in sq miles); converted here. Not for design floods but for safety checks. |
Note: Lacy's (likely Lacey's) formula is not included as it pertains to regime channel design (e.g., wetted perimeter P = 4.75 √Q) rather than estimating peak flood discharge from catchment characteristics. Consult local hydrological data or IS codes for precise C values and validations. These are empirical and should be used with site-specific calibration.
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