Storm Surge Height Estimator
Estimates storm surge height using the empirical SLOSH-based approach, accounting for wind speed, storm size, forward speed, approach angle, and coastal shelf slope.
Formula
H_surge = H_base × A_bathy × A_forward × A_angle × A_slope
Base Wind Setup (H_base):
H_base = (Cd × ρair × V2 × L) / (ρwater × g × d)
- Cd = wind drag coefficient (0.0012–0.0018, speed-dependent)
- ρair = 1.225 kg/m³, ρwater = 1025 kg/m³
- V = maximum sustained wind speed (m/s)
- L = fetch length = radius of maximum winds (m)
- g = 9.81 m/s², d = nearshore water depth (m)
Amplification Factors:
- A_bathy = √(dref / d) — shoaling amplification (dref = 10 m)
- A_forward = 1 + 0.005 × Vforward — forward speed enhancement
- A_angle = sin(θ) — approach angle (θ = 90° = perpendicular = maximum surge)
- A_slope = (Sref / S)0.25 — shelf slope factor (Sref = 1/1000)
Assumptions & References
- Based on the wind setup equation derived from depth-integrated momentum balance (Pugh, 1987).
- Amplification factors follow SLOSH (Sea, Lake, and Overland Surges from Hurricanes) model principles (Jelesnianski et al., 1992, NOAA Technical Report NWS 48).
- Drag coefficient Cd is wind-speed dependent per Large & Pond (1981): 0.0012 (<25 m/s), 0.0015 (25–50 m/s), 0.0018 (>50 m/s).
- Bathymetric shoaling follows Green’s Law approximation for long-wave amplification over a sloping shelf.
- Forward speed enhancement reflects the asymmetric intensification of surge on the right-front quadrant (for Northern Hemisphere storms).
- This is an empirical estimate only. Actual surge depends on storm track, coastal geometry, tidal phase, and local topography. Use NOAA’s official SLOSH or ADCIRC models for emergency planning.
- Does not account for wave setup, astronomical tide, or freshwater runoff contributions.
- Saffir-Simpson wind speed thresholds per NHC (2012).