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Post-fire hillslope erosion using an Unmanned Aerial Vehicle (UAV) with on-ground sediment analysis

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Author(s): Nicholas Hager

Document Type: M.S. Thesis
Publisher: California State University, Northridge
Published Year: 2018
Pages: 136
DOI Identifier: 10211.3/203473
ISBN Identifier:

Hillslopes are susceptible to accelerated erosion following fire. Vegetation loss encourages slope destabilization during and following rain events, with resultant soil erosion. Between July 22, 2016 and August 9, 2016, the Sand Fire burned nearly 168 km2 (64 mi2) southeast of Santa Clarita increasing soil erosion and deposition in the nearby Pacoima Reservoir. This thesis focused on erosion within Maple Canyon, part of the larger Pacoima watershed that ultimately drains into the Pacoima reservoir. Data collection used a combination of sediment traps to monitor changing soil properties and aerial imaging techniques to measure overall hillslope sediment loss. Sediment deposition was observed using fifteen sediment traps set across the project site. The resultant data were used to explore sediment erosion rates and patterns on individual hillslopes across various slope angles and aspects. Sediment samples were collected at each of the fifteen soil traps in the study period of four months and analyzed for moisture and particle attributes including sorting, skewness, and graphic mean. Lastly, topographic change was monitored and used as a surrogate for calculating the volume of eroded sediment on the hillsides of Maple Canyon using a technique called Structure from Motion (SfM), to create 3-dimensional models from an Unmanned Aerial Vehicle (UAV). There was a substantial increase in sediment erosion on hillslopes greater than 30° and, as expected rates of soil loss were much higher before vegetation regeneration. It was documented also, that owing to the high temperature of the fire, the voluminous production of ash and development of a hydrophobic layer decreased the infiltration capacity of the weathered bedrock, thus encouraging accelerated surface runoff. It was calculated that 26,472 cubic meters (440,444.5 ft3) of sediment loss occurred within Maple Canyon between the dates of December 13, 2016 and April 6th, 2017. The research documents erosion rates and processes shortly after a high intensity chaparral fire using traditional sediment capture techniques. When coupled with the use of a UAV platform together with SfM and GIS, topographic change and the calculation of erosion from post-fire hillslopes proves valuable to help predict catchment and reservoir capacities.

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In Text Citation:
Hager (2018) or (Hager, 2018)

References Citation:
Hager, N., 2018, Post-fire hillslope erosion using an Unmanned Aerial Vehicle (UAV) with on-ground sediment analysis: M.S. Thesis, California State University, Northridge, 136 p., doi: 10211.3/203473.