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Center for Spatial Information and Research

Nearshore Effects of Shoreline Protection on Aquatic Habitat in the Winnebago Pool Lakes

As conditions conducive to aquatic macrophytes continue to deteriorate in the Winnebago Pool Lakes, a cascade of system wide effects may be expected to occur. The lakes within the system are uniformly shallow with broad, unprotected expanses exposed to the wind. Because of the largely agricultural watershed, the system has been subjected to high external loading of nutrients, resulting in a hypereutrophic state. As biomass and productivity of phytoplankton have increased, water clarity has decreased, favoring phytoplankton over aquatic macrophytes. Coupled with the loss of mid water emergents, particularly common reed grass, wave action has increased. The shallowness and long fetch with regard to the direction of summer prevailing winds in these lakes prevent seasonal thermal stratification, causing greater wind induced turbidity and internal nutrient loading, and also increased rates of shoreline erosion through exposure to higher wave energy.

The shoreline recession and deposition of fine material in shoreline locales has instigated a response by shore property owners, particularly those with residences, to protect existing shorelines. This has largely been accomplished by armoring eroding shores and, in some cases, shoreline wetlands, with shore protection devices such as rip rap. For example, a recent survey of shoreline residents in Winnebago County found that 72% of the respondents had some form of shore protection on their property (Gabriel, 1998). This management procedure has been implemented without regard or knowledge of ecological effects. Similarly, a 1998 shoreline erosion inventory conducted by the Winnebago County Land and Water Conservation Department found that 91% of the county's shoreline with adjacent wetlands needed shore protection. Because of the widespread acceptance and low cost of this technique, it is currently being applied system wide, the results being changes in shoreline composition with possible losses of shoreline habitat diversity and isolation of shoreline wetlands from lakes.

Our goal was to ecologically characterize the structural and functional aspects of protected and unprotected wetland shorelines in the Winnebago System. To address the potential ecological effects that the conversion of shorelines from fine, soft material protected by emergent plants to hardened substrate composed of limestone rip rap has, we compared physical characteristics and plant and animal communities between natural and hardened shorelines in both a temporal and a spatial context. This was accomplished by identifying adjacent lengths of physically comparable shorelines that exhibit natural conditions, that had been rip rapped, and that have been protected by offshore protection structures.

We established three related objectives:

1) Develop a historical, quantified record of changes in the spatial characteristics of typical protected and unprotected shorelines on the Winnebago System, including lake and river shorelines;

2) Develop baseline information on protected and unprotected wetlands, comparing vegetation types, utilization by fish and benthic macroinvertebrates, and physical and chemical characteristics such as bathymetry, wave attenuation, water clarity, sediment composition and sedimentation,and temperature;

3) Assess the relationship between unprotected or protected wetland shorelines and environmental conditions, including vegetation, habitat, and physical/chemical factors.

Outcomes:

1) A historical, quantified record of changes in the spatial characteristics of characteristic protected and unprotected shorelines on the Winnebago System;

2) Development of on site techniques for assessing the current state of health of wetland shorelines applicable to wetland shorelines in other shallow lakes in Wisconsin;

3) Development of spatially explicit maps detailing bathymetry, substrate type, and location and kind of vegetation found in the vicinity of protected and unprotected wetland shorelines and an assessment of the relation of the shoreline types to these factors;

4) Determination of the effects of shoreline protection on physical and chemical environmental conditions including wave energy, sedimentation, substrate composition, water temperature, and dissolved oxygen conditions;

5) Determination and comparison of the kinds of fishes and benthic macroinvertebrates that use unprotected and protected wetland shorelines;

6) An integrative, conceptual ecological community based model that describes the relation between protected and unprotected wetland shorelines, the associated plants and animals, and environmental conditions, including physical and chemical factors;

Funding Sources:

 Wisconsin DNR Shallow Lakes Funding Program Grant Amount: $45,000
Dates of Project: 07/99 - 09/02
Summer Students Funded: 5

Finished Reports:

Gabriel, A.O., and L. Bodensteiner. 2003. Nearshore Effects of Offshore Protection Structures on Aquatic Habitat in the Winnebago Pool Lakes, Wisconsin. Wisconsin Department of Natural Resources Shallow Lakes Program Report. Geo-ecology Research Group Research Report 7. Volumes 1 and 2. Ellensburg: Central Washington University. 334 pp.

Gabriel, A.O., and L. Bodensteiner. 2002. Nearshore Effects of Shoreline Protection on Aquatic Habitat in the Winnebago Pool Lakes, Wisconsin. Wisconsin Department of Natural Resources Shallow Lakes Program Report. Geo-ecology Research Group Research Report 5. Ellensburg: Central Washington University. 154 pp.

Related Publications:

Gabriel, A.O., and L. Bodensteiner. 2004. Nearshore effects of offshore protection structures on aquatic habitat, Winnebago Pool Lakes, Wisconsin. Presented at the International Society of Wetland Scientists 25th Annual Conference, Seattle, Washington, July 18-23, 2004.

Bodensteiner, L.R., and A.O. Gabriel. 2003. Nearshore effects of shore protection on aquatic habitat in the Winnebago Pool Lakes, Wisconsin. Presented at the Washington Lake Protection Association 16th Annual Conference on Lakes, Reservoirs and Watersheds, Chelan, Washington, April 2-4, 2003.

Lemke, J., L.R. Bodensteiner, and A.O. Gabriel. 2002. The effects of wetland restoration breakwaters on water quality and fish communities in two Wisconsin lakes. Presented at the 15th Washington Lake Protection Association Annual Conference on Lakes, Reservoirs and Watersheds, Olympia, Washington, April 4-7, 2002