Developing a Decision Support System to Improve Transportation Planning in Landslide Prone Terrain

Within the past decade, several transportation planning decision support systems that combine heuristic programming techniques with geographic information systems (GIS) technology have been developed to meet forest operation challenges. These decision support systems, however, have not directly addressed the upslope influences of landslides in choosing routes from road networks. This paper provides an overview of an on-going research project that seeks to develop a decision support system that takes slope stability into account when selecting transportation routes. The advancement of GIS and heuristic tools to assist planners in the location of transportation corridors may yield significant benefits in reducing short and long term costs associated with route selection and transportation networks. INTRODUCTION Transporting wood products from the forest to the mill is among the largest costs associated with wood production. Costs are usually divided between activities that are associated with forest roads including road construction, costs affiliated with operating and maintaining vehicles, and fixed and variable maintenance costs (Sessions 1986). Other influential factors include road network design and construction, network efficiency in meeting operation goals, and road maintenance. Usually, transportation planning methods have required forest engineers to use contour maps to identify combinations of route alternatives. These alternatives are then ranked on construction, transport, and maintenance requirements. While this method presents a feasible, yet labor intensive, method for smaller forested landscapes, larger areas pose significant challenges. These challenges may limit the ability of planners to develop a full set of alternatives and to choose from a set of alternatives in an efficient and timely manner. Past research efforts in forest operations and transportation planning have concentrated on individual route projection and evaluation. While these efforts have addressed gradients in locating road networks and optimal routes, they have typically not addressed whether routes on landslide prone terrain are being selected and they do not consider risk of slope failure. This paper describes an on-going project that is investigating the use of heuristic programming techniques and a GIS to create a decision support system for optimizing route selection based on topographic constraints. Our objective in this preliminary description of project efforts is to characterize the relative stability of a road network in steep terrain while accounting for the impacts of culverts and roads on hydrologic flow paths. In our initial tests, we have used a