STWAVE 8.1 MODEL

Bathymetry

A bathymetry file for Lake Mendota is required for STWAVE analysis.  Bathymetry is the measurement of depth in a body of water.  The Lake Mendota bathymetry was obtained from Chris Petykowski, a UW-Madison graduate student.  Over 6,400 measured bathymetry points (x, y, & z coordinates) were used to construct Lake Mendota in STWAVE 8.1.  The resultant figure of Lake Mendota is illustrated below.  The bathymetry points within the square depicts the Yahara River outlet area; the location that will be simulated with STWAVE 8.1.

Subsequently, wind speed, significant wave height, and the significant wave period parameters are required to run STWAVE simulations. 

Wind Speed

Typical wind speed for Lake Mendota were established from NOAA for a 15 year duration (1987-2002) from the Madison Dane County Regional Airport.  The daily average wind speed (U₁₀) was computed to be approximately 4.2 m/s.  The daily wind direction suggested that northern winds are more prevalent, followed by southeast and east winds.  However, north winds will not be considered in this study because STWAVE only functions on a half plane.  Thus, it can not calculate refraction from the north in a southward direction.  East, south, and west winds will all be observed, with emphasis on the results from southeast winds (the second most prevalent wind direction). 

Significant Wave Height (Hs) and Wave Period (Ts)

The significant wave height and wave period were calculated using the SMB METHOD:

*  Assuming a storm duration of 4 hours

            Example Calculations for U₁₀ = 4.2 m/sec

Three wind speeds were applied in the STWAVE analysis (4.2, 8, and 16 m/sec.).  The significant wave heights and periods were computed.

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