Recently, we were approached by the Driftless Area Land Conservancy to create several maps for their planning of a hiking trail network in southern Wisconsin. The proposed 50 mile backpacking and hiking trail would connect Tower Hill, Governor Dodge, and Blue Mounds State Parks, and create access for hikers, birders, and anglers to explore and enjoy the unique and natural beauty of Driftless Area.
The maps we produced highlighted the geography, landscape, land use, and significant cultural locations surrounding the three state parks within the proposed project area. The project also included a corridor analysis to determine an "optimal corridor" the parks and several cultural locations, and to help identify land parcels suitable for trail access and construction. The analysis, as a whole, highlights the appropriateness of a given area for a particular use based on physical and intrinsic characteristics and is used in environmental, conservation, and urban studies to determine the most suitable site locations, or corridors, for habitat, buildings, transportation routes, and utilities. While utilizing a least cost path technique, the corridor analysis involves more than just the optimal route between two locations, it also considers the accumulative effects of each input variable in a way that can reduce the negative impacts for a given area.
Table 1, Cost Surface Algorithm and Parameters (below).
Map 1, Land Cover Suitability (below left). Map 2, Cultural Location Density (below right).
Map 3, Slope Suitability (below left). Map 4, Combined Cost Surface (below right).
The analysis is based on three model inputs and their rankings; land cover, cultural (POI) connectivity density, and slope. Other inputs, such a soils, and even ridge lines were considered, but we settled on the three. Each input was graded on their importance to trail location. A cost surface map was then produced by assigning weights to each of the inputs and combining their scores (Table 1, Map 4).
For the current model, we assigned weightings of 75% for land cover, 15% for cultural connectivity, and 10% for slope. We presumed that land cover (Map 1) was the most important factor for trail placement, with forested and grassland areas having the greatest influence (urban/water having the least). The cultural connectivity density surface (Map 2) was constructed from the density of lines extending from each POI to every other POI. The closer the points are to each other, the denser the connectivity will be. The density surface was ordered into five classes by the natural breaks method, with cultural suitability decreasing as the density decreased. The slope surface (Map 3) rankings were determined from a digital elevation model (DEM). Slope was calculated and ordered into five classes (from flat to steep), with trail suitability decreasing as the percent slope increased.
The final result (Map 5) contains the proposed trail segments and buffered trail corridors, which can be used to select intersecting parcel data containing land owner and land use type. [The trail corridor is a 1000 foot buffer (yellow on map) surrounding the model generated least cost path (proposed path)]. This is just one scenario as the analysis can be tweaked in many different ways. Even a slight change in the weighting of inputs can significantly alter the outcome of suitable trail location.
Map 5, Proposed trail corridors (below).
Please visit the Driftless Area Land Conservancy website for more information about what they do and what they have to offer.