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Debris Flow
NOTE: Debris Flow risk attributes are located in the "Channel" data type part of NetMap Portal.
The debris flow attribute provides an index of debris flow susceptibility along steep headwater streams (higher values = higher susceptibility). The attribute is based on the model of Miller and Burnett (2008) and governing variables include the number of shallow landslide sites that trigger a debris flow, headwater channel steepness, its confinement and angles of tributary confluences. The index, a probability of susceptibility of channels to debris flow movement, scour and deposition, is an empirical model calibrated for the Oregon Coast Range. However, it should provide a approximate index for debris flows in most mountain terrains. See Warning about using Slope Stability Models.
If these attributes are not available for your own watershed, please contact us. See more.
Figure. Downstream sequences of debris flow susceptibilities in headwater streams (A) can be used to differentiate one debris flow prone headwater stream from another (low-high might warrant more caution compared to high – low). The susceptibility of headwater streams immediately above a larger, fish bearing channel (B) can also be used to differentiate debris flow potential and possible impacts to larger channels. The downstream sequence of predicted susceptibilities can be used to estimate the likelihood of debris flows reaching a specified channel segment, such as fish habitat. For example, a headwater - upstream to downstream sequence debris flow susceptibility of low – high – low would be less of a concern compared to the sequence of low – moderate – high or moderate – high or simply overall high (A). In addition, one should focus on the predicted debris flow susceptibility of the segment located immediately upstream of the low- to high-order debris flow prone confluence. Headwater segments with high susceptibility immediately upstream of the confluence with a larger fish-bearing stream is of more concern compared to headwater segments with a lower susceptibility (B).