SEWRPC has mapped the key elements of the natural resource base of the Southeastern Wisconsin Region: lakes, streams, and associated shorelands and floodlands; wetlands; woodlands; wildlife habitat areas; areas of rugged terrain and high-relief topography; wet, poorly drained, and organic soils; and remnant prairies. In addition, SEWRPC has mapped such natural resource-related features as existing and potential park sites, sites of historic and archaeological value, areas possessing scenic vistas or viewpoints, and areas of scientific value. These inventories have resulted in the delineation of environmental corridors, which are broadly defined as linear areas in the landscape containing concentrations of these significant natural resource and resource-related features. The delineation process is technically defined in this article.
More specifically, SEWRPC has identified what have come to be termed “primary environmental corridors,” “secondary environmental corridors,” and “isolated natural resource areas.” Primary environmental corridors are concentrations of significant natural resources at least 400 acres in area, at least two miles in length, and at least 200 feet in width. Secondary environmental corridors are concentrations of significant natural resources at least 100 acres in area and at least one mile in length. Isolated natural resource areas are those remaining significant natural resources at least five acres in area and at least 200 feet in width.
In 2000 primary environmental corridors totaled about 462 square miles or 17 percent of the Region. Secondary environmental corridors totaled an additional 75 square miles, or slightly less than three percent of the Region, while isolated natural resource areas totaled about 63 square miles, or slightly greater than two percent of the Region. In total, then, environmental corridors and isolated natural resource areas comprised about 600 square miles or about 22 percent of the Region.
The SEWRPC regional land use plan recommends that steps be taken by State, county, and local governments to preserve and protect these important concentrations of remaining natural resources in the Region for the reasons outlined in this article. It is recommended that the lowland portions of environmental corridors and isolated natural resource areas--areas that are floodplains and wetlands--not be filled and be kept free from future urban development of any kind. It is further recommended that the upland portions of primary environmental corridors be preserved and protected, ensuring that the lands are not developed for urban purposes except for residential use at a density no greater than one unit per five acres. Finally, the plan recommends that county and local governments give consideration to similarly protecting the upland portions of secondary environmental corridors and isolated natural resource areas as local needs and conditions may warrant. Guidelines for corridor use are set forth here.
Implementation of the foregoing environmental corridor protection recommendations is envisioned to come about primarily through enactment of appropriate zoning regulations at the county and local levels of government. In addition, the Wisconsin Department of Natural Resources and the Wisconsin Department of Commerce seek to bring about the specific recommendations related to protection of the primary environmental corridors in the discharge of their responsibilities attendant to public and private sanitary sewer extension approvals. Essentially, the operational rules of those Departments require that the primary environmental corridor protection and development density recommendations, as set forth in the SEWRPC regional land use plan, be met before State approval of sewer extensions. This State policy can have the effect of imposing more stringent development limitations than set forth in local zoning regulations.
Inventories undertaken in 2000 indicated that, in one way or another, about 426 square miles of primary environmental corridor was protected and preserved through ownership and/or public land use regulation. This totals about 92 percent of the primary corridor area. The unprotected primary corridor areas are highlighted on this map.
SEWRPC inventories of natural resource features and delineations of environmentally sensitive lands are carried out in desk-top analyses using the best available orthophotography. The delineations are always held out, however, as subject to field verification. Because of the importance of these delineations, State, county, and local governments frequently call upon the SEWRPC staff to verify and stake in the field the boundaries of such environmentally sensitive lands. Information on accessing field services is provided here.