CCFHR: Wave Exposure Model (WEMo)

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Wave Exposure Model (WEMo)

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ISSUE: Hydrodynamic factors profoundly impact the environment of coastal areas. Wind waves, particularly waves associated with storms, are unpredictable and can pose dangerous situations under which to collect scientifically empirical, comparative information. Unfortunately, there are few simple–to–use, inexpensive tools that can provide a quantitative value of wave exposure. Such a tool is needed by resource managers who need to estimate wave energy in coastal regions or in inland waters to gauge susceptibility of developed areas. This tool is also needed by scientists who desire a quantitative measure of wave effects to relate to ecosystem function.

APPROACH: CCFHR scientists have developed a numerical wave exposure model (WEMo) that operates in two modes. The first mode, Representative Wave Energy (RWE), uses linear wave theory to calculate actual wave height and derived wave energy while taking into consideration wind generation and local water depth characteristics such as shoaling and dissipation from breaking waves. The second mode, Relative Exposure Index, uses directional wind speed, frequency of wind, and fetch data in addition to water depth collected at a site to calculate how exposed that site is to wind–generated waves in comparison to any other site. Sites with a higher REI experience greater wave energy. REI is also useful for comparison with older studies that used this technique.

Figure 1. WEMo REI output for Core and Bogue Sounds, North Carolina.

OUTCOME: WEMo is being applied to a number of geographic areas including Tampa Bay, FL, Chesapeake Bay, MD & VA, Core Sound and New River, NC, and Prince William Sound, AK. Figure 1 (right) is WEMo REI output of the top 5% extreme wind speeds from 2001–2004 for Core and Bogue Sounds in NC. Red colors represent the highest REI values.

Ongoing work involves validation of WEMo by verifying model output with data collected by wave sensors installed at various locations. The following forecasting applications can be addressed with WEMo:

Forecasting

seagrass exclusion areas (i.e., areas where wave energy is too high for persistent seagrass habitat);
the potential for restoration of seagrass;
submersed and shoreline habitat landscape pattern;
shoreline susceptibility to hurricanes and other extreme wind events;
effect of shoreline structures on habitat;
behavior of oil spills and guiding mitigation (clean up) strategies.

Downloads

Wave Exposure Model (WEMo), version 3.0
Version 3.0 (updated October 2007): Available on the WEMo downloads and requirements page

By using this software tool, you indicate your awareness of and consent to the following terms and conditions of use:
Information provided from this software tool is NOT intended to be used for decisions involving human safety and welfare risks. The developers of this program—the National Oceanic and Atmospheric Administration—assume no responsibility and can not be held liable for any end use of this software. For your own protection, please label all output with "NOT FOR USE INVOLVING HUMAN SAFETY AND WELFARE."
Wave Exposure Model (WEMo) Manual
Version 3.0, October 2007: WEMo was modified in this version (WEMo 3.0) to calculate wave height and derived Representative Wave Energy along with the relative index (REI) calculated in older WEMo versions.
Citation for this work: Tech Memo: NOS NCCOS 65, WEMo (Wave Exposure Model): Formulation, Procedures and Validation
This report describes the working of National Centers for Coastal Ocean Service’s WEMo, capable of predicting the exposure of a site in estuarine and closed water to local wind–generated waves.