Wednesday, September 17, 2014

Antarctica, Sea Level and Santa Barbara

UC Santa Barbara sits atop a marine terrace bounded by sea cliffs 40 to 50 feet high.
Santa Barbara  Airport is in the background. Photo © UCSB Photo Services.
In prior posts (June 9; May 20) I presented some of the factors of predicted global sea level rise and Antarctica’s role in it. If a reader were to accept the sea level rise projections of the IPCC and other scientific authorities, they might ask, “What will be the impact on me and my family, and what can be done about this?”

If you live in Kansas you might not bother to think about sea level rise (even though disruption of major U.S. ports will affect you), but I live in Santa Barbara and I do think about it. The City of Santa Barbara also has been thinking about sea level rise. The California Energy Commission commissioned a report completed in 20121 that evaluated what Santa Barbara faces from ongoing and accelerating sea level rise and what can be done about it.

Santa Barbara is an idyllic small city 90 miles north and a cultural world away from Los Angeles. Wealthy people like to come here to live and retire, to enjoy the sea and the coastal mountains in usually fine weather. Besides the wealthy there are the majority of Santa Barbarans who have lived here for a generation or more and know their good fortune. The coastline of the city is gem-like. It consists of long stretches of beaches that for the most part are bounded by cliffs – except near the Santa Barbara Airport in Goleta and downtown Santa Barbara. These areas lie behind wide beaches with parks. Downtown tourist hotels and a seaside drive frame the beach there. The elevation of the airport and much of downtown is near current sea level.

The report uses projected sea level rise as set by the State of California, which mostly follows IPCC scenarios for the 21st century2. The report assumes that sea level rise cannot be stopped in this century, even if mitigation of CO2 emissions could slow it to some degree. It considers what will be the impact of 14 inches of rise by 2050 and 47 inches by 2100. It discusses what the City could do to prepare for the collection of impacts – how the City could adapt.

These impacts include flooding of low areas during storm surges, in particular during El Niño events, damage to shoreline infrastructure from increased wave action (due to Global Warming), sea cliff erosion, beach erosion, and inundation of low elevation areas (permanent flooding). By mid century wave damage to shoreline structures is considered the highest threat. Cliff retreat could claim several homes.

By end century sea cliff erosion and inundation present the most extreme challenges, but shoreline damage will intensify as well. Specific predicted outcomes are permanent flooding of the Santa Barbara airport, permanent flooding of a large area of downtown Santa Barbara, permanent flooding of the low areas of the 101 freeway and underpasses, retreat of shoreline into the lower downtown area (beyond the El Estero Wastewater Treatment plant and the Desalination facility), and retreat of cliffs by several hundred feet. Cliff top homes are the most expensive in Santa Barbara if not California. By end century dozens of these properties could be gone.

Adaptations scenarios are identified in the report. My interpretations of the possible actions presented in the report are (pages 75-76):

Flooding and Inundation adaptation: Redesign and retrofit (raise) structures; raise airport runways; increase building setbacks from shoreline, deny rebuilding permits after storm damage; construct temporary sea walls (they will need to be moved as sea level rises).

Beach erosion adaptation: Do nothing - let the beach migrate inland; or attempt to stabilize by resupply of beaches with imported sand; build retention structures (currently not allowed in most cases).

Wave damage adaptation: Armor the coastline (currently rarely approved by the CA Coastal Commission); managed retreat of infrastructure from shoreline (move roads and freeway).

Cliff erosion adaptation: relocate housing; increase building permit shoreline setbacks over time; control cliff erosion by limiting runoff and drainage. Most cliff failure is from above. Armoring the cliff base with riprap has not proven effective because of this fact.

An action plan is possible and practical. Costs versus benefits need to be evaluated. Will we begin?

Of course Santa Barbara is not the only U.S. coastal city that has to face the sleeping giant of sea level rise. Here's what the U.S. National Climate Assessment has to say about what is at risk for our nation;

"More than 5,790 square miles and more than $1 trillion of property and structures are at risk of inundation from sea level rise of two feet above current sea level – an elevation which could be reached by 2050 under a high rate of sea level rise of approximately 6.6 feet by 2100, 20 years later assuming a lower rate of rise (4 feet by 2100) (Ch. 2: Our Changing Climate), and sooner in areas of rapid land subsidence."

The authors of the Santa Barbara report offer this provocative statement in their conclusion,
“Adaptations to longterm problems involve longterm investments and they also require the consideration of intergenerational equity and other social and economic factors that significantly affect the calculation of costs and benefits.”

1- Griggs, Gary, and Nicole L. Russell (University of California, Santa Cruz). 2012. City of Santa Barbara SeaLevel Rise Vulnerability Study. California Energy Commission. Publication number: CEC5002012039.

2- Church, J.A., P.U. Clark, A. Cazenave, J.M. Gregory, S. Jevrejeva, A. Levermann, M.A. Merrifield, G.A. Milne, R.S. Nerem, P.D. Nunn, A.J. Payne, W.T. Pfeffer, D. Stammer and A.S. Unnikrishnan, 2013: Sea Level Change. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

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