Thursday, November 16, 2006 - 8:55 AM

A GIS-Based High Resolution Flow Channel and Wet Area Mapping Approach for Soil and Water Protection in Forest Operations Planning.

Paul N.C. Murphy, Daniel J. Vega Nieva, Fan-Rui Meng, Mark Castonguay, Jae Ogilvie, and Paul A. Arp. Forestry and Environmental Management, UNB, 28 Dineen Drive, Fredericton, NB E3B6C2, Canada

Flow channel and wet area maps, generated from digital elevation models (DEMs) and existing hydrographic data layers using a GIS process, can be used as an effective planning tool to reduce impacts of forest operations on soil and water such as channeling of water flow, soil rutting and erosion and stream siltation.  High resolution (1 m) LiDAR and lower resolution (5-10 m) conventional DEMs were used. The maps were ground-truthed using a number of methods in two Canadian case studies: one in New Brunswick (mixed wood Acadian forests) and another in Alberta (hilly boreal forest). 88 % of stream culvert locations predicted by the map fell within 40 m of actual locations in New Brunswick and 94 % in Alberta. The projected depth to water from the soil surface, used to map wet areas, was found to be positively related to actual depth to water along transects adjacent to wetlands in New Brunswick, and this index was also related to the sphagnum boundary around wetlands. Across New Brunswick, 89 % of wetlands in the provincial wetland inventory were nested within the projected 0 – 0.5 m depth to water class, and this was further verified through multi-temporal RADARSAT image analysis. The index was related to the soil moisture regime of the Alberta Vegetation Inventory. Extent of rutting fields in harvested areas corresponded with projected extent of wet areas. Actual rutting depths were related to predicted rutting depths, derived from soil cone penetration resistance, tire-based ground pressures of the logging machines, soil moisture and temperature conditions, and soil parameters (texture, organic matter and coarse fragment content). LiDAR DEMs offer even greater resolution and accuracy of soil hydrologic conditions than conventional DEMs, further enhancing operational planning.