Luke A. McGuire Haiyan Wei Francis K. Rengers Hoshin Gupta Lin Ji David C. Goodrich Taojun Liu 2021 <div class="abstract-group"><div class="article-section__content en main"><p>Extreme hydrologic responses following wildfires can lead to floods and debris flows with costly economic and societal impacts. Process-based hydrologic and geomorphic models used to predict the downstream impacts of wildfire must account for temporal changes in hydrologic parameters related to the generation and subsequent routing of infiltration-excess overland flow across the landscape. However, we lack quantitative relationships showing how parameters change with time-since-burning, particularly at the watershed scale. To assess variations in best-fit hydrologic parameters with time, we used the KINEROS2 hydrological model to explore temporal changes in hillslope saturated hydraulic conductivity (<i>K</i>_sh) and channel hydraulic roughness (<i>n</i>_c) following a wildfire in the upper Arroyo Seco watershed (41.5&nbsp;km²), which burned during the 2009 Station fire in the San Gabriel Mountains, California, USA. This study explored runoff-producing storms between 2008 and 2014 to infer watershed hydraulic properties by calibrating the model to observations at the watershed outlet. Modelling indicates<span>&nbsp;</span><i>K</i>_sh<span>&nbsp;</span>is lowest in the first year following the fire and then increases at an average rate of approximately 4.2 mm/h/year during the first 5 years of recovery. The estimated values for<span>&nbsp;</span><i>K</i>_sh<span>&nbsp;</span>in the first year following the fire are similar to those obtained in previous studies on smaller watersheds (&lt;1.5&nbsp;km²) following the Station fire, suggesting hydrologic changes detected here can be applied to lower-order watersheds. Hydraulic roughness,<span>&nbsp;</span><i>n</i>_c, was lowest in the first year following the fire, but increased by a factor of 2 after 1&nbsp;year of recovery. Post-fire observations suggest changes in<span>&nbsp;</span><i>n</i>_c<span>&nbsp;</span>are due to changes in grain roughness and vegetation in channels. These results provide quantitative constraints on the magnitude of fire-induced hydrologic changes following severe wildfires in chaparral-dominated ecosystems as well as the timing of hydrologic recovery.</p></div></div> application/pdf 10.1002/hyp.14208 en Wiley The timing and magnitude of changes to Hortonian overland flow at the watershed scale during the post-fire recovery process article