Roads
Of the hundreds of miles of unpaved roads, which segments present the greatest threat from accelerated runoff and sediment to the stream network?
Which road-stream crossings, if they were a barrier to fish migration, would block the most usable fish habitat?
Which road segments are located in floodplains, areas most prone to flood damage?
Which road segments are located in potentially unstable terrain?
See Forest Road Tool Storymap
Do you know the answers in your own watershed?
If not, NetMap tools and virtual watersheds can help.
Road Surface Erosion and Sediment Delivery
NetMap contains three road surface erosion and sediment delivery models:
1) Road Erosion and Delivery Index (READI)
2) WEPP Roads
3) GRAIP-Lite
READI is a new GIS-based model to assess road erosion and delivery of water and sediment from road networks to streams. READI quantifies the effectiveness of existing road surfacing and drain placement in reducing road sediment delivery and guides upgrades to optimize future reductions.
Although all unpaved road surfaces produce sediment, only a small proportion delivers sediment to stream channels.
READI parses a GIS road layer, using a DEM, into high and low points and identifies the population of naturally occurring drain points and the individual channel reaches they drain into.
READI also accepts a GIS point shape file of GPS engineered road drain locations to improve predictions of road runoff to streams.
READI optimizes the location of new surfacing (native soil to rocked) to maximize reductions in sediment delivery. The majority of predicted sediment reduction occurs in a small proportion of new surfacing locations.
READI optimizes the location of new drains to maximize reductions in sediment delivery. The majority of predicted sediment reduction occurs in a small proportion of the new optimized drain locations.
Habitat Length above Road-Stream Crossings
NetMap tools are used to quickly calculate the distance of usable fish habitat across all road-stream crossings for anadromous and resident species.
Identify Road Segments in Floodplains
NetMap tools are used to quickly calculate the distance of usable fish habitat across all road-stream crossings for anadromous and resident species. First, the floodplain tool delineates floodplains at different elevations above the channel, and then the GIS road layer is overlaid, identifying likely road-floodplain intersections.
NetMap tools for slope stability screening (shallow landslides, debris flows, gully and flash floods) can be used in conjunction with GIS road layers in a virtual watershed.
See the Slope Stability and Wildfire web pages.