The ART maps shows the extent of water inundation from over-topping of the Bay only. The extreme tide elevations associated with each storm scenario are worst-case scenarios, assuming storms coincide with the highest tide of the day. The mapping shows the increase in ocean surface elevation caused by low atmospheric pressure and wind fetch i.e. storm surge. It does not account for wind-driven wave action or the effects of storm water runoff (from our land, pipes and drainage systems, for example) during storm events and may therefore underestimate total water levels during storm events.
The mapping does not account for the pumping capacity of the pumps installed in Belvedere lagoon. However, the volume of water inundation that would result from shoreline over-topping (as opposed to storm water runoff) would vastly overwhelm said pumping defenses.
The mapping does not consider climate change factors that may increase the frequency and severity of large storm events over time. Storm surge trends associated with climate change are not yet clear for Northern California. The topic is an area of active research.
The ART mapping tool is not the only coastal flood web tool available. A list of relevant tools can be found here. ART was selected because it is the most up-to-date, locally-relevant tool that leverages FEMA’s hydrodynamic modeling of the San Francisco Bay and utilizes local planner knowledge of current flooding hot spots.