CONCLUSION Conclusion Collaboration: Sea-level Marin Adaptation significantly impact all residents and tourists Response Team’s (C-SMART) sea level rise traveling this portion of the coast during high tides, vulnerability assessment examined the exposure, as few alternative routes are available. Buildings, sensitivity and adaptive capacity of built and or land surrounding buildings, that flood near daily, natural assets. Many of Marin’s essential and or even only during annual storms, are not likely to beloved coastal community assets are vulnerable sustain the expense and trauma from reoccurring to sea level rise. flood damage. This is especially a concern for the Calles and Patios neighborhoods in Stinson Beach In their current conditions and without intervention, and Tomales Bay homes that are not elevated to the most vulnerable coastal Marin assets are accommodate higher waters and waves. beaches and buildings on or near the water’s dynamic edge. Maps 83-87 and the following sections highlight major vulnerabilities by onset, or timing, for roughly 2030, 2050, and 2100. IMPACTS AT-A-GLANCE: SCENARIO 2 1,681 acres 2030 Expectations (Scenarios 1 & 2) flooded @ MHHW 3,000+ residents plus + annual storm tourists o Beaches, underground on-site surge wastewater treatment systems (OWTS), buildings, and streets in Stinson Beach 2,054 acres 110 569 acres Calles and Patios neighborhoods. flooded @ MHHW agricultural of o Shoreline Highway between Stinson +20-year storm acres aquaculture Beach and Bolinas, the Walker Creek surge (mostly ranch) crossing in Marshall, and bridges on 588 homes & Middle Road and Valley Ford Lincoln businesses could School Road. flood, 60 could o Beaches and beach front and downtown suffer from buildings and streets in Bolinas. erosion o Septic systems, beaches, marshes, and Property Owners buildings along the eastern and western $561 million in County of Marin shores of Tomales Bay. assessed Caltrans o The water distribution pipe underneath property value Bolinas Public Utility Shoreline Highway and Sir Francis Drake Stinson Beach Water 2.3 miles of wet Boulevard serving Inverness residents. Fire Districts road, o Intertidal rocky lands off Muir Beach and National Parks Service 2 ports, Duxbury Reef in Bolinas. California State Parks 1 marina, o Fire service facilities and tsunami AT&T evacuation routes in Stinson Beach. 1 boat launch o Recreational facilities at Dillon Beach Beaches Resort and Lawson’s Landing. Tidal Marshes o Blufftop buildings in Muir Beach, Bolinas, Eelgrass beds and Dillon Beach may be vulnerable to Estuaries accelerated erosion. These small pockets of flooding along the coast could result, at best, in daily road and recreation facilities closures. Consistent erosion exacerbated by higher tides and storm surges could take out portions of the roads for longer periods of time and may require repair. This level of damage would Marin Coast Sea Level Rise Vulnerability Assessment Page 183 CONCLUSION Map 83 Southern Marin Coast 2030 Sea Level Rise and Storm Surge Expectations Marin Coast Sea Level Rise Vulnerability Assessment Page 184 CONCLUSION Map 83. Northern Marin Coast 2030 Sea Level Rise and Storm Surge Expectations Marin Coast Sea Level Rise Vulnerability Assessment Page 185 CONCLUSION Mid Century Expectations (Scenario 3) The following places could face chronic and storm surge flooding and erosion at twenty inches of sea level and a 20-year storm surge by 2050. o Locations presented in near-term scenarios 1 and 2. o Seadrift neighborhood in Stinson Beach. o Bluff top homes in Muir Beach, Bolinas, and Dillon Beach. o Olema-Bolinas Road, the only road to Bolinas. o Additional buildings and streets in downtown Bolinas, including the historic district. o Bolinas Public Utilities District lift station at the end of Wharf Road. o The Bolinas Wye and local roads in Seadrift neighborhood, Stinson Beach. Credit: CDA Stinson Beach west of State Route 1 could face tidal flooding, including Calle del Arroyo, the access road to nearly all IMPACTS AT-A-GLANCE: SCENARIO 3 lower Stinson Beach homes. 2,062 acres o Shoreline Highway in Stinson Beach, Pt. flooded @ MHHW 3,000+ residents plus Reyes Station and East Shore at creek + 20-year storm tourists crossings, and low lying segments of Sir surge Francis Drake Boulevard in Inverness could prevent through access. 680 homes, businesses, & o Public access sites along these roads 172 569 acres institutions could would be compromised. agricultural of flood, 148 could acres aquaculture By mid-century, near-term impacts will continue to suffer from (mostly ranch) worsen and reach to new areas in Bolinas, Stinson erosion Beach, and around Tomales Bay. Over water housing may not be feasible without significant $793 million in alterations. Road closures could last longer and assessed repeated flooding could cause even greater property value damage. By this time period, significant alterations Property Owners to the roadways maybe necessary to maintain 5 miles of wet County of Marin through access and avoid frequent and costly road, Caltrans repairs. Underground utilities in Stinson Beach 1 port, Bolinas Public Utility and around Tomales Bay may become 1 marina, Stinson Beach Water overburdened by higher waters and lose 1 boat launch Fire Districts National Parks Service functionality, requiring conversion to other systems Beaches to ensure remaining homes are livable. Beaches California State Parks Tidal Marshes AT&T would be severely eroded and bluff collapse an Creeks even greater risk than in the near-term. These Eelgrass beds closures would significantly impact existing and Estuaries new residents and tourists that would have major ripple effects on the West Marin economy. Marin Coast Sea Level Rise Vulnerability Assessment Page 186 CONCLUSION Map 84. Southern Marin Coast 2050 Sea Level Rise and Storm Surge Expectations Marin Coast Sea Level Rise Vulnerability Assessment Page 187 CONCLUSION Map 85. Northern Marin Coast 2050 Sea Level Rise and Storm Surge Expectations Marin Coast Sea Level Rise Vulnerability Assessment Page 188 CONCLUSION End of Century Expectations (Scenarios 4 & 5) IMPACTS AT-A-GLANCE: SCENARIO 5 By 2100, higher high tides at 80 inches of sea 2,772 acres 3,000+ residents plus level rise could adversely impact the locations flooded @ MHHW tourists flooded in the near- and medium-terms, and significant portions of the areas that previously 2,846 acres 457 569 acres only suffered storm surge flooding. Tidal flooding flooded @ MHHW agricultural of would reach beyond State Route 1 and Sir Francis +100-year storm acres aquaculture Drake Boulevard in low-lying areas. Daily tidal surge (mostly ranch) flooding at 40 inches, or about 3.5 feet, of sea 1,075 buildings level rise could reach 850 parcels, 400 buildings, could flood, 719 and 7 miles of road. With a 100-year storm surge could suffer from an additional 300 parcels, 450 buildings, and 7.4 erosion miles of road would also flood. $855.4 million in Property Owners At 80 inches, or about 6.5 feet of sea level rise, assessed County of Marin 1 1,220 parcels, 1,060 buildings, and 17 miles of property value Caltrans road could face tidal flooding. A 100-year storm 18 miles of wet Bolinas Public Utility surge could flood these areas and further inland, road, Stinson Beach Water and an additional 1,300 parcels, and a total of 1 port, Fire Districts 1,075 buildings and 18 miles of road, including all 1 marina, National Parks Service low-lying areas in Muir Beach, Stinson Beach, 1 boat launch California State Parks Bolinas, Inverness, and East Shore, effected. The AT&T damage would be exacerbated by storm water Beaches flowing down the hills into the ocean or bay. Tidal Marshes Destroyed building stock could compromise over Creeks $300 million (2015 dollars) in assessed value. Eelgrass beds Vulnerable single family homes amount to $855 Estuaries million in market value (2015 dollars). In addition, bluff erosion could destroy several hundred buildings in Muir Beach, Bolinas, and Dillion Beach. Below is a list of additional areas that could be flooded. o Locations presented in near- and medium- term scenarios 1, 2, and 3 would only see more frequent and severe flooding if they still exist. o Shoreline Highway through East Shore. o Buildings in Inverness west of Sir Francis Drake Boulevard. o Downtown Bolinas up to Brighton Road, including the market, library, community center, gas station, museum, historic buildings and other valued places. At this level and frequency of flooding, many of the vulnerable properties and roadways could not exist in their current state. Thus, completely changing West Marin’s look, feel, livability, Inverness Yacht Club septic system covers. Credit: S. Callow economic activity, and accessibility; warranting a forward thinking examination of and funding for adaptation measures well before these risks arise. 1 2016 dollars Marin Coast Sea Level Rise Vulnerability Assessment Page 189 CONCLUSION Map 86. Southern Marin Coast Long-term Sea Level Rise and Storm Surge Expectations Marin Coast Sea Level Rise Vulnerability Assessment Page 190 CONCLUSION Map 87. Northern Marin Coast Long-term Sea Level Rise and Storm Surge Expectations Marin Coast Sea Level Rise Vulnerability Assessment Page 191 CONCLUSION Flooding from sea level rise could reduce side septic leach lines to the east side of useable living space; adversely affect tourism, Shoreline Highway and away from Tomales Bay transportation, and natural attractions and in Marshall. resources, and homes and businesses. The most vulnerable built areas are the Calles and Implementing additional adaptation measures Patios neighborhoods, along the shoreline of may require new institutional, legal, and Bolinas Lagoon and Bolinas beach front, and on financing arrangements, engineering measures, the shallows and shores of Tomales Bay. In and other incremental actions property owners East Shore, nearly all development is vulnerable can take. These measures and sea levels on the by the medium-term. coast must be monitored and evaluated to inform need and effectiveness of these types of More than 3,000 existing residents, hundreds of strategies.