SECTION 5.4037. Hazard Module - Storm Surge and Wave Model

(a) Before an applicable storm, the association must take steps so that it will be able to obtain rapid, post-event high-resolution surge and wave modeling to provide surge and wave time histories.

(b) The surge and wave hazard module must directly incorporate both numerical modeling and the high-resolution aerial photographs and LIDAR measurements required under §5.4036(a) and (b) of this title.

(c) The technical features of the storm surge and wave model must include:

(1) a domain of surge and wave modeling that extends from at least Pensacola, Florida to the Mexican coast at latitude 23 degrees north, and at minimum, 500 km offshore of Texas;

(2) for Texas and parts of Louisiana west of longitude 93.5 degrees west, sufficiently high-resolution nearshore and overland to show dunes and other significant features impeding flow, such as a grid with 50 meter or finer resolution (resolution may be coarser offshore and in other locations), with models run on the same grid, if possible, to avoid interpolation errors;

(3) the same wind field used to compute wind damage, which must be a best available reanalysis wind field that incorporates measurements made during the applicable storm;

(4) a drag coefficient that features a high wind cutoff that is defensible from observations or the scientific literature;

(5) wave computations that use a third-generation unsteady spectral wave model that has been tested closely against data from Hurricane Ike and other storms in Texas;

(6) wave computations that include feedback from velocities and water levels generated by the surge model;

(7) wave breaking dissipation that is spectrally based and does not use a simple depth-limited cutoff;

(8) a shallow water model (either depth-averaged or multilevel) that includes convective processes and bottom friction that varies with substrate or vegetation;

(9) tides as an integral part of the model;

(10) the ability to produce initial estimates within 48 hours of landfall;

(11) the ability to readily incorporate new LIDAR topographical data into the grid, and wind data into the surge and wave model as it becomes available post-event, to rapidly produce improved surge and wave model simulations;

(12) the ability to quickly produce estimates of waves and surge as additional data becomes available, and pass these estimates to the association for use in the damage estimation module;

(13) the ability to compare model estimates with measured wave and water level data as it becomes available; and

(14) the ability to produce error estimates for each applicable storm.

(d) The association must take steps to minimize errors between model estimates and the observed storm surge and wave heights measured during an applicable storm.

Source Note: The provisions of this §5.4037 adopted to be effective March 28, 2017, 42 TexReg 1459