The Geomorphic Road Analysis and Inventory Package (GRAIP) is a comprehensive free road inventory and modeling tool used to analyze the hydrogeomorphic impacts of roads on forested watersheds and to help land managers efficiently evaluate the multiple aspects of risk created by forest roads. GRAIP combines a detailed field road inventory and powerful GIS analysis tools to predict the amount and location of road sediment production and delivery, mass wasting risk from gullies and landslides, risks of stream crossing failures, infrastructure maintenance needs, and road hydrologic connectivity.
GRAIP couples detailed road inventories with a set of powerful GIS tools to support roads analysis, which can be locally calibrated in a repeatable fashion and with minimal effort. The full scope of GRAIP includes methods to inventory roads, analyze forest road impacts, and to measure road surface erosion from sample sites.
The field protocol systematically inventories a road system using GPS and automated data forms. Once GPS data are downloaded and converted to the correct format, they can be run through a data quality checking program and the errors can be corrected. Quality checked and corrected data can then be analyzed in a program implemented in ArcGIS. The program produces maps of road surface erosion, accumulated road sediment in streams, and contributing length by road segment and drainage location, which relate directly to slope stability and gullying risks. The inventory and program also provide analyses relating to stream diversion and failure potential and consequences, culvert maintenance needs, and optionally fish passage.
GRAIP has several advantages over other approaches to predicting the impacts of roads on natural resources. GRAIP excels at helping managers prioritize BMP and restoration decisions. The GPS inventory geolocates the road and drainage infrastructure and directly observes evidence of stream connection at each place where sediment leaves the road; the GIS output shows the magnitude of risk at these locations.
GRAIP is able to use locally developed erosion rates to predict sediment production and delivery on a local basis. The road inventory data that are collected are updatable and useful for documenting changing watershed conditions.
The output of GRAIP can be easily displayed in the form of maps showing areas of high sediment delivery to channels, and the road segments and drainage features that lead to the elevated risk. This simplifies the assimilation of the information by managers, and facilitates the use of the information in prioritization decisions, development of treatment alternatives, and monitoring of road treatments.
GRAIP_Lite uses DEMs, already existing road GIS layers with surfacing type information, and a small field calibration dataset to determine 6th code subwatershed scale road sediment production and delivery. Road layers are broken into GRAIP-style segments. Production is calculated in the usual GRAIP way, and delivery is based on the flow distance from the road to the stream and the calibrated probability of delivery at that distance. GRAIP_Lite is good at narrowing a large potential project area to the smaller watersheds with the most sediment problems.
GRAIP road inventory data
Digital Elevation Model (DEM), UTM, 1 arc-second
Watershed landslide initiation points layer (optional)
Locally developed road surface erosion base rate
Road, drainage, and stream shapefiles and raster grids that contain predictions regarding the amount and location of road sediment production and delivery, mass wasting risk from gullies and landslides, risks of stream crossing plugging, fish passage at stream crossings (optional), and road hydrologic connectivity.
These outputs can be combined with other field observations already a part of the inventory data to evaluate existing mass wasting and road infrastructure conditions. It is easy to then display this data in the form of maps showing areas of high sediment delivery to channels and the road segments and drainage features that lead to the elevated risk.
For more information, including the GRAIP manuals, an FAQ, case studies, a roads photo gallery, and upcoming opportunities for GRAIP training, see the GRAIP website, here.
GRAIP is a collaborative joint venture between the U.S. Forest Service Rocky Mountain Research Station and Utah State University. RMRS staff supports GRAIP from the Boise Aquatic Sciences Lab. GRAIP has an active user community that includes partners inside and outside of public land management and regulatory agencies, including: the Environmental Protection Agency, the Bureau of Land Management, the Nez Perce Tribe, the Nature Conservancy, Idaho Department of Environmental Quality, the Southwest Crown of the Continent Collaborative, Coos Watershed Association, Idaho Forest Restoration Partnership, the U.S. Geological Survey, the Wilderness Society, and the Great Northern Landscape Conservation Cooperative.