Coastal Storms Program: Oregon Coastal Inundation Visualization Tool-Model Information

Coastal Storms Program: Oregon Coastal Inundation Visualization Tool

Oregon Coastal Inundation Visualization Tool Model Calculation Information

The following illustration and equations explain the foredune erosion model and wave runup calculation that are used in the mapping application. The runup elevation of storm waves can assist in calculating the amount of erosion that might occur to a beach or property as a result of a storm. For the Oregon coast model, the wave runup values are dependent on the deepwater wave height, among other physical factors.

Foredune Erosion Model

The illustration below shows the foredune erosion model and how it is calculated. Total water level, the sum of the measured tide (E_t) and the runup of waves (R) on the beach, compared with the elevation (E_j) of the toe of the foredunes are presented.
[drawing: shows the total water level, the sum of the measured tide (Et) and the runup of waves (R) on the beach, compared with the elevation (Ej) of the toe of the foredunes]

Calculating Wave Runup

Total water lever (runup) = R + E_T, where R is the wave runup height and E_T is the measured tide level. In this application E_T data are collected real-time from the NOAA Center for Operational Oceanographic Products and Services (CO-OPS).

Potential erosional conditions are assumed to occur when 2% of wave runup maxima, represented as R_2%, reach or exceed the elevation of the beach-face junction.

The formula that represents these conditions is

R_2% = 0.27(SHL)^1/2

where

R_2% is the 2% exceedance value of runup maxima

S = Slope (a value taken from beach profiles)

H = Deep water wave height (collected real-time from the National Data Buoy Center)

L = Deep water wave length

L = (g/2π)², where g = gravity (9.8 meters per second²) and T = wave period (collected real-time from the National Data Buoy Center)

Source: Ruggiero, P.; Komar, P.D.; McDougal, W.G.; Marra, J.J.; and Beach, R.A., 2001. Wave runup, extreme water levels and the erosion of properties backing beaches. Journal of Coastal Research, 17(2), 407-419. (PDF, 3.5 MB). Note: This document is in Portable Document Format (PDF). Download Adobe® Reader to view the document.