Landslides/Debris Flow Risk

Step Wise Guide

Erosion

· Which locations (such as buildings on alluvial fans) are most susceptible to debris flow impacts?

Refer to the "Warning" button in the tool interface. Follow up any remote sensing work, including using NetMap, with field work to verify environmental conditions and landslide and debris flow risk. There is never zero risk, there is only degrees of risk, which often is best considered on a relative basis.

Structures located in areas of high relief and steep hillslopes may be susceptible to debris flow impacts. Of potential concern are fans located at the base of steep headwater tributaries (1^st and 2^nd Strahler [1952] order) as well as along tributary channels with steep, dissected hillslopes located in the headwaters above them. Estimating landslide and debris flow risk, either to stream channels or to structures and roads, requires geotechnical expertise. NetMap provides coarse grained screening information from which to consider the likelihood of debris flow impacts to particular locations. Field work that determines actual landslide and debris flow risk is required to best estimate the risk posed by debris flows.

Step 1: Go to NetMap Erosion Tools > Channelized Mass Wasting > Debris Flows. Display the “debris flow susceptibility-reaches” or “debris flow susceptibility-junctions” data to examine the spatial variation in potential (provisional) debris flow susceptibility across your watershed or landscape. Read thoroughly the Technical Help Guide on the various slope stability attributes, including debris flows. Follow up any remote sensing work, including using NetMap, with field work to verify environmental conditions and landslide and debris flow risk. There is never zero risk, there is only degrees of risk, which often is best considered on a relative basis.