Prediction of Channel Response Areas due to Wildfire Disturbance using GIS and TauDEM Karen Williams GIS in Water Resources

Project Objective Use spatial distribution of channel, network, and landscape characteristics to predict channel areas most likely to respond to wildfire disturbance Stream power Channel slope Hillslope gradient Burn severity Stream order Land cover

Geomorphic Disturbance and Response Disturbance regime: Landscape processes that influence the “supply, storage, and transport of water, sediment, and wood” (Benda et al, 1998) Examples: wildfire, mass wasting, timber harvest Response to disturbance varies with channel type, basin morphometry, land cover and use

Dutch Creek

Project Watershed: Dutch Creek Basin area = 28 sq.mi. Drains southwest to North Fork Flathead River

Project data 10 m. cell size elevation raster data Stream vector data Land cover raster data Burn severity raster data All obtained from Glacier NP GIS person

Methods Stream network (demnet) - TauDEM Compared to streams layer from GNP Created network includes more low order channels Stream order raster (demord) - TauDEM Channel slope – TauDEM Slope between links reported in demnet Classify slopes by Montgomery and Buffington (1997) <2% = response reach 2-4% = transport reach > 4% = source reach Hillslope gradient – DEM raster toTIN Burn severity and land cover - GNP

Comparison of TauDEM and Glacier NP stream vector data Glacier NP stream vector data created from 1:24,000 maps, digital orthoquads and aerial photos TauDEM created more low order streams Low order, ephemeral channels are conduits for sediment and wood delivery

Land cover raster data Mostly coniferous forest High severity burn in riparian coniferous forest increases frequency and extent of woody debris delivered to channel

Hillslope Gradient and Channel Slope Much of watershed is moderate slope Areas of steep hillslopes are more likely to be subject to mass wasting

Fire History: Anaconda 1999, Moose 2001, WolfGun 2003

2001

2003

Methods Stream power, Channel slope, S Discharge, Q The ability of channel to do work, power per unit length Channel slope, S Option in TauDEM: Define a feature class of nodes at which slope will be calculated Discharge, Q Assume the two-yr recurrence interval flood approximates the channel forming (dominant discharge) Q2 For this region, Q2 = A^.918 * P^1.33 A = area in sq.mi; P = mean annual precip., in. Determine Q2 at each node

Mean annual precipitation polygon 5 precipitation zones in watershed Contributing area at each node apportioned by precipitation zone

Stream power and channel slope Areas of high stream power not necessarily correlated with channel slope Not enough nodes to be conclusive

Stream power at nodes and stream order Some nodes of high stream power occur where low order and higher order channels confluence

Based on spatial distribution of basin and channel characteristics, the identified channel areas of severe burn, moderate hillslope gradient, and moderate to high stream power may exhibit a response

Thanks to Glacier NP Dave Tarboton Questions? Thanks to Glacier NP Dave Tarboton