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2021 Multijurisdictional Local Hazard Mitigation Plan  Historical hydrologic patterns can no longer be solely relied upon to forecast the water future.  Precipitation and runoff patterns are changing, increasing the uncertainty for water supply and quality, flood management and ecosystem functions.  Extreme climatic events will become more frequent, necessitating improvement in flood protection, drought preparedness and emergency response. The amount of snow is critical for water supply and environmental needs, but so is the timing of snowmelt runoff into rivers and streams. Rising snowlines caused by climate change will allow more mountain areas to contribute to peak storm runoff. Changes in watershed vegetation and soil moisture conditions will likewise change runoff and recharge patterns. As stream flows and velocities change, erosion patterns will also change, altering channel shapes and depths, possibly increasing sedimentation behind dams, and affecting habitat and water quality. With potential increases in the frequency and intensity of wildfires due to climate change, there is potential for more floods following fire, which increase sediment loads and water quality impacts. The California 4th Climate Assessment predicts that intense atmospheric rivers will occur more frequently as mean temperatures rise. Exposure, Sensitivity and Vulnerability The following summarizes changes in exposure and vulnerability to the flood hazard resulting from climate change:  Population and Property—Population and property exposure and vulnerability may increase as a result of climate change impacts on the flood hazard. Runoff patterns may change, resulting in flooding in areas where it has not previously occurred.  Critical facilities—Critical facility exposure and vulnerability may increase as a result of climate change impacts on the flood hazard. Runoff patterns may change, resulting in risk to facilities that have not historically been at risk from flooding. Changes in the management and design of flood protection critical facilities may be needed as additional stress is placed on these systems. Planners will need to factor a new level of safety into the design, operation, and regulation of flood protection facilities such as dams, bypass channels and levees, as well as the design of local sewers and storm drains.  Environment—The exposure and vulnerability of the environment may increase as a result of climate change impacts on the flood hazard. Changes in the timing and frequency of flood events may have broader ecosystem impacts that alter the ability of already stressed species to survive. 17.2.5 Landslide Climate Change Impacts on the Hazard Climate change may impact storm patterns, increasing the probability of more frequent, intense storms with varying duration. Increase in global temperature is likely to affect the snowpack and its ability to hold and store water. Warming temperatures also could increase the occurrence and duration of droughts, which would increase the probability of wildfire, reducing the vegetation that helps to support steep slopes. Each these factors would increase the probability of landslides. In Bay Area hills, the risk of landslides is a function of the interaction between precipitation, soil conditions, and seismic activity. Climate change creates increased likelihood of extreme precipitation and wildfire events; both create increased risk of slope failures for the coming century. (California 4th Climate Assessment, 2019). 17-14