30 ENVIRONMENTAL CONNECTION / THIRD QUARTER 2025 / IECA.ORG By Alicia M. Kinoshita, Ph.D.; Danielle S. Hunt, M.S. Urban Stream Management: Fire, Arundo Donax And Geomorphic Impacts The escalating severity of wildfire seasons in California highlights the urgent need for effective land and water resource management. Fires in urban riverine systems can threaten lives and infrastructure while severely impacting stream health and stability; specifically, post-fire flooding and sediment transport can degrade essential drinking and recreational water sources.1,2 While immediate post-fire impacts on surface hydrology such as sedimentation and flooding are welldocumented, studies in semi-arid urban systems, where human activities significantly alter natural fire and hydrological regimes, remain limited. In addition to geomorphic changes that affect erosion control, water quality and sediment dynamics, urban fires can create additional strain on limited firefighting resources. This issue is exemplified by the 2018 California wildfire season, which required the simultaneous efforts of nearly 10,000 firefighters and the significant utilization of out-of-state resources.3 To effectively address post-fire geomorphic changes in urban streams, practical researchbased insights into fire and vegetation management strategies are needed to support the development of resilient urban water systems. In 2024, the number of fires was within the five-year average, but the number of acres burned was over five times the average due to increases in flammable vegetation that spread fire.4,5 In semi-arid urban stream systems in southern California, elevated year-round water levels contribute to increased nutrient loads and more frequent flash floods. These conditions encourage the infestation of flammable invasive vegetation, which alters erosion patterns and streambank stability.6,7 UNIVERSITY PARTNER PEER REVIEW Figure 1. Top image: 8 June 2018 burned riparian and hillslope. Middle image: 29 June 2018 burned riparian and hillslope with giant reed and palm regrowth in the riparian, Bottom image: 26 April 2019 non-native vegetation dominates post-fire site.
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