Utilization of the Distributed-Hydrology-Soil-Vegetation-Model (DHSVM) To Quantify Streamflow Changes and Slope Failure Probability Following the Snow-Talon Fire Near Lincoln Montana, USA

Models are commonly used to attempt to simulate complex interactions on the landscape. Many factors such as vegetation, soils, topography, weather and disturbances can influence the hydrology of a watershed. Understanding what is influencing changes in streamflow following fire can be difficult due to lack of data or models running at inappropriate resolution. In dealing with the large spatial extent of approximately 37,000 acres burned at the Snow-Talon Fire near Lincoln Montana and heterogeneous landscape characteristics it is difficult to know the specific regions where mitigation efforts should be focused or what specific influencing factors may be affecting the watershed hydrology. In this study, the Distributed-Hydrology-Soil-Vegetation-Model (DHSVM) was used to identify regions of higher soil failure probability and estimates of pre and post-disturbance stream flows. Because DHSVM is a physically-based distributed parameter model it allowed for the use of high resolution data that more accurately represented landscape parameters such as soils, vegetation, slope, and fire severity. Weather inputs into the model were represented in three-hour increments from two SNOTEL stations and one RAWS. Using the data at a scale of 30 meter pixels, weather at three hour increments and physically based water flux calculations, a detailed simulation of how water moves through the landscape could be visualized. Areas of high soil failure probability can be identified at a per pixel basis. Specific stream reaches can be assessed for maximum expected stream flows. Working with high spatial resolution data as inputs for DHSVM allowed for results of failure probabilities to be seen at the 30 meter resolution of the digital elevation model. Steamflow values were modeled at 3 hour intervals simulating the influence of daily weather and the varying mosaics of fire disturbance, vegetation types and soils. The ability of DHSVM to model streamflow during calibration was shown in Nash-Sutcliffe efficiency coefficients values of .29 for Blackfoot near Lincoln gauge and to .81 for the Blackfoot below Alice Creek gauge. Simulated peak streamflow following fire increased 66% from the pre-fire conditions