A field study in Lake Wingra was conducted on November 17 and 21, 2006. The study included a sub bottom profile of the lake sediments, shelby tube sediment samples, and observations of waves.

1. Sub Bottom Profile

Sub bottom profiling is a geophysical technique that uses acoustic waves to map lake bathymetry and sediment layering. The sub bottom profiler (SBP) uses a frequency of 200 kHz to map the lake bathymetry, and a frequency of 20 kHz to obtain sediment layering data.

Figure 3. A schematic drawing of a sub bottom profiler. (From http://www.tritech.co.uk)

The SBP was mounted on a boat and fully submerged into the water, and data was collected on a laptop aboard the boat. A PVC pipe was used to stabilize the SBP while the boat was in motion. Several survey lines were taken parallel and perpendicular to the shoreline both inside and outside the exclosure in order to get a complete coverage of the exclosure area.  The SBP was also coupled with global positioning system to determine exact location of the surveys.

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Figure 4. (a) The approximate location of the survey lines for the sub bottom profile with the red lines indicating the first day of surveying and the green lines the second.  (b) The sub bottom profiler used for surveying.  (c) The sub bottom profiler in use  (d) The laptop used to collect the SBP data.

2.Shelby Tube Sampling

Shelby tubes are thin walled tubes used to collect undisturbed sediment samples. The Shelby tube was connected to a steel rod and adaptor, which was lowered into the sediment vertically, then removed from the water with the sediment intact in the tube. 14 Shelby tube samples were taken, 6 inside the exclosure and 8 outside the exclosure. The samples were used for density and water content analysis, as well as erosion tests.

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Figure 5. (a) The approximate locations of the Shelby tube samples. (b) The Shelby tube and the connecting components. (c) Collecting the samples (d) Kevin and the samples after they were capped and sealed.

3. Wave climate observations

Pictures were taken using a digital camera to compare the wave climate inside the exclosure to the wave climate outside of the exclosure. The pictures can be viewed in the data analysis page.