Analysis of Wind-Wave Characteristics in Lake Superior

Background information

Project objectives

Approaches

Data and result

Conclusion

References

Background information about lake superior:

            Lake Superior is the largest of the Great Lakes in surface area and volume. Lake Superior could contain all the other Great Lakes plus three more lakes the size of Lake Erie. Water flows into the lake from many small rivers and streams. The Long Lac and Ogoki diversions in Canada channel water into Lake Superior that would otherwise flow into Hudson Bay. By order of the International Joint Commission, the lake's level, controlled by gates on the St. Marys River at Sault Ste. Marie, may not exceed 602 ft (183 m) above sea level. Each year a small percentage of the lake's water flows out through the St. Marys River, and it takes almost two centuries for the water to be completely replaced (retention time). The Lake Superior drainage basin is rich in natural resources and scenic beauty. It is very populated and economically dependent on its natural resources, which include metals, minerals, forests and recreation/tourism opportunities such as national lakeshores and national/state/provincial parks. It is particularly known for its clear, cold water and agate beaches. A circle tour guides highway travelers around the lakeshore. Many shipwrecks in Lake Superior are now protected in bottomland preserves and accessible to recreational divers. In 1985, scientists using a submersible vessel descended for the first time to the deepest part (-1,333 ft./-405 m) of Lake Superior near the Pictured Rocks National Lakeshore in Michigan waters.

More Details of Lake Superior:

LENGTH:  350 miles / 563 km.
 
BREADTH:  160 miles / 257 km.
 
AVERAGE DEPTH:  483 ft. / 147 m.
 
MAXIMUM DEPTH:  1,332 ft. / 406 m.
 
VOLUME:  2,900 cubic miles / 12,100 cubic km.
 
WATER SURFACE AREA:  31,700 sq. miles / 82,100 sq. km.
 
DRAINAGE BASIN AREA:  49,300 sq. miles / 127,700 sq. km.
 
SHORELINE LENGTH (including islands):  2,726 miles / 4,385 km.
 
ELEVATION:  600 ft. / 183 m.
 
OUTLET:  St. Marys River to Lake Huron
 
RETENTION/REPLACEMENT TIME:  191 years

References: Lake Superior brochure, 1990, Michigan Sea Grant

Project Objectives:

1.      To obtain the wave climate data including wind direction, wind speed, water depth, and wave height in Lake superior and regenerate it into a proper form

2.      To use simple wave hindcasting method in order to transform deep water wave heights into shallow water wave heights

3.      To use wave transformation theory to obtain wave shoaling, wave refraction, and wave braking information along some parts of the shore in Lake superior

4.      To map the transformation of waves using topographic maps that are available

Approaches to Project Objectives:

I. Wave climate data

            This data has been collected from (1) NOAA bouy station 45006 from 1908 to 2000 (2) NOAA C-Man DISW3 station from 1983 to 2000, and (3) the wave hindcast dataset from 1956 to 1987 which was collected from the USACE WIS ftp website. For water depth information for each station, it can be obtained from the USACE website also. To obtain this data, we have to go to these websites and download all the data, which is not in a proper form; therefore we have to regenerate this data into the form that we can use properly. In order to check which stations will be used in the project, we have to find stations that will have deepwater wave information by calculating the ratio between water depth and wave length if it is more than 0.5 then we can use that data. We then will plot wave height in meters versus time in days for each station in a one-year interval of time to see what the highest value of significant wave height of each year is, and it should be nearly the same for each station in each year. Then we will use our engineering judgments to see which data we will use to proceed into the next step.

Websites to obtain wave climate data:

Station DISW3:

            Then we plot this data out using the wave program I created to see which values of wave height and wave period we should use for analysis purpose:

II. Simple wave hindcasting

            For stations that do not have wave height data, we need to do wind wave hindcasting in order to get the wave height. In this manner, we will consider only the period of highest wind speed for that station in each year.  We will use JONSWAP method in this computation.

III. Wave Transformation

            After we gain the wave height data for the near shore, we can compute the direction and wave height of waves corresponding to the area we are interested. We will consider wave shoaling, wave refraction, and wave braking.

Wave breaking:

Mapping: Poplar NE

Conclusion:

1.  Climatic Data from station must be manipulated in order to use it to do analysis for wave transformation

2. Checking which data is usable such as shallow water or deep water

3. Choosing the most accurate way and engineering decision to do wave transformation calculation

4. Mapping is done in small sections and can be put together to create a big picture of wave characteristics in a specific area

References:

Sorensen, Robert M. (1997), Basic coastal engineering , New York : Chapman & Hall.

Kamphuis, JW (2000), Introduction to Coastal Engineering and Management, World Scientific Publishing

University of Wisconsin-Madison Map Library.  Topographic maps for water depth data.  1954, 1973, 1978.