Tuesday, October 9, 2007

Sea Level Rise in a Countywide Plan

In a previous article I questioned whether my home county of Marin was looking closely enough at the impacts of sea level rise on the local built environment including homes, businesses and transportation routes. After having read through the latest draft of our new Countywide Plan, I feel a bit more at ease. I'm not sure if I had much to do with the incorporation of these statements, having grilled one of the county planners about the department's consideration of this elephant under the carpet, but at least the Plan acknowledges the looming danger. It does not, though, make any definitive declarations of zoning changes or plans for levee development. Such changes, when sea level rise is regarded as a conceptual future risk, would no doubt create a political firestorm with business owners, homeowners and Marin's lucrative real estate industry.

Again, I'll go on record to say that nothing in the Plan acknowledges the potential of amplifying feedbacks to speed up sea level rise beyond one meter by the year 2100. The next iteration of the Plan will surely include a reassessment. So here are a few excerpts from the Countywide Plan that other county governments might be interested in seeing:

The Role of Science
Achieving and maintaining sustainability requires keeping up with science. At times, land use and other public policy decisions operate within an institutional framework that does not reflect current scientific information. This is understandable as cutting edge science is always on the move. For example, the multiple causes and effects of climate change, described below, are now well established and current land use decision-making needs to reflect the link between fossil fuel consumption and sea level rise. Keeping up with science is an underlying principle of this Plan. Towards that end, employing evidencebased strategies combined with up-to-date scientific knowledge will provide sound guidelines for taking care of the land, our communities, and the generations that will follow us.
Are threats from environmental hazards increasing?
Many structures lie in hazardous areas, and land for new development may be even more hazardprone. With most easily buildable land already developed, construction increasingly is being proposed on the remaining marginal lots with difficult access and steep hillsides which are subject to slope instability and are vulnerable to rapid changes in fire behavior. Bluff erosion is threatening coastal homes built when bluff edges seemed safely distant. Vegetation that can fuel fires has increased because
natural fires have been suppressed, and residential development continues to encroach on wildlands. Proliferation of impermeable surfaces, alteration of natural drainage patterns, and the effects of climate change have increased the frequency and severity of flood events, and estimates indicate that sea level could rise as much as 36 inches by 2100. Maps 2-9 through 2-15 are utilized by the County in reviewing land use activities proposed in areas with hazard potential.
EH-3.3 Monitor Environmental Change. Consider cumulative impacts to hydrological conditions, including alterations in drainage patterns and the potential for a rise in sea level, when processing development applications in watersheds with floodin or inundation potential.

With increases in sea level due to global warming, flooding is predicted to increase in the future. Locating development in flood-prone areas can expose structures to damage and create risks for inhabitants in the immediate and surrounding areas.
EH-3.k Anticipate Sea Level Rise. Work with the U.S. Geological Survey, the San Francisco Bay Conservation and Development Commission, and other monitoring agencies to track bay and ocean levels; utilize estimates for mean sea level rise to map potential areas subject to future inundation (including by updating information about watershed channel conditions and levee elevations); and amend the Development Code to incorporate construction standards consistent with the policies of BCDS’s Bay Plan for any areas subject to increased flooding from a rise in sea level.
EH-3.l Limit Seawall Barriers. Limit repair, replacement, or construction of coastal sea walls and erosion barriers consistent with Local Coastal Program requirements, and as demonstrated to be necessary to protect persons and properties from rising sea level.

EH-3.n Plan for Sea Level Rise. Consider sea level rise in future countywide and community plan efforts. Consider revising Marin County Development Code standards for new construction and substantial remodels to limit building or require elevated buildings and infrastructure or other applicable mitigations in areas that may be threatened by future sea level rise as shown on maps released by the San Francisco Bay Conservation and Development Commission in February 2007.
EH-3.o Seek Levee Assistance. Pursue funding for levee reconstruction in those areas threatened by sea level rise, including but not limited to Santa Venetia.

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