Res21 16010 final - Laserfiche WebLink

Browse Search

13. SEA LEVEL RISE 13.1 GENERAL BACKGROUND Sea-level rise is caused primarily by two factors related to global warming: the added water from melting ice sheets and glaciers; and the expansion of seawater as it warms. In the past century, global mean sea level has increased by 7 to 8 inches, with human influence the dominant cause of observed atmospheric and oceanic warming. Given current trends in greenhouse gas emissions and increasing global temperatures, sea level rise is expected to accelerate in the coming decades, with scientists projecting an increase in sea level in the San Francisco area by 2100 of anywhere from 1.0 to 10.2 feet (California Natural Resources Agency, 2018). The most damaging events over the next few decades are likely to be dominated by large El Niño-driven storm events in combination with high tides and large waves. Impacts will generally become more fr equent and more severe in the latter half of this century. 13.2 HAZARD PROFILE San Mateo County is highly vulnerable to the effects of rising sea levels. If left unmanaged, future flooding and coastal erosion could pose considerable risks to life, safety, critical facilities, the County’s natural and recreational assets, and the economy. The assessed value of parcels in the project area exposed to near-term (present-day) flooding exceeds $1 billion, and the assessed value of parcels exposed to erosion and flooding in the long term (50–100 years) totals nearly $40 billion. More than 30,000 residential parcels and 3,000 commercial parcels may also be vulnerable in the long term (County of San Mateo, 2018). Flooding, erosion, and sea level rise directly threaten people and property in the sea level rise hazard areas. They also have indirect effects on all communities in the County, even those on high ground, because assets and infrastructure in the sea level rise areas provide critical services and functions to communities outside these areas. The County is already exposed to coastal flooding when large rain events coincide with high tides on the San Francisco Bay, making it imperative to take steps to reduce risk (County of San Mateo, 2018). 13.2.1 Previous Documents and Resources County of San Mateo Sea Level Rise Vulnerability Assessment The County of San Mateo’s 2018 Sea Level Rise Vulnerability Assessment used best available existing data to assess the County’s vulnerability to sea level rise. It supports a sea level rise preparedness strategy that does the following (County of San Mateo, 2018):  Identifies risks to life and safety 13-1