Two years ago, research by the University of Hawai`i\u2019s School of Ocean and Earth Science and Technology (SOEST) revealed that flooding from the combination of a one-meter rise in sea level and a hurricane or a tsunami could affect 80 percent of the economy located between Pearl Harbor and Waikiki, with the total cost of those impacts reaching into the tens of billions of dollars.<\/p>\n
Now, as part of the statewide effort to prepare a Sea Level Rise Vulnerability Assessment and Adaptation Report (SLR report) by the end of next year as required under 2014\u2019s Act 83, SOEST researchers have been focusing their sea-level-rise modeling efforts on areas outside Honolulu\u2019s urban core, looking not at tsunami or storm surge-related flooding, but that associated with groundwater inundation, coastal erosion, seasonal (non-storm) wave inundation, and a 100-year coastal flooding event. Using their modeling results, consulting and engineering firm Tetra Tech has been analyzing the potential social and economic impacts, census block by census block.<\/p>\n
Last month at a sea level rise vulnerability and adaptation workshop sponsored by the state Department of Lands and Natural Resources, the state Office of Planning, SOEST and UH Sea Grant, Tetra Tech\u2019s Catherine \u201cKitty\u201d Courtney and SOEST associate dean Chip Fletcher provided a sobering glimpse of what could be in store for O\u2019ahu\u2019s `Ewa Beach, which already has a narrow, chronically eroding shoreline.<\/p>\n
Over the last decade or so, the `Ewa Beach population has grown by 50 percent to about 64,000 residents and most homes there have been built at ground level, Fletcher said. With an anticipated 1.06-foot rise in sea level by 2050, the area will lose $29.63 million worth of land and buildings to coastal erosion, according to Courtney\u2019s presentation. By 2100, when sea level is expected to have risen by 3.2 feet, which is roughly one meter, the land and building losses due to coastal erosion will total $54.88 million.<\/p>\n
As for temporary losses due to seasonal wave run-up and a 100-year flood, Courtney reported that the costs would be $10.2 million (347 structures) and $56.7 million (1,308 structures), respectively.<\/p>\n
In total, 1,295 households in `Ewa Beach will be lost due to coastal flooding by 2100, displacing more than 5,000 people, she found.<\/p>\n
Costly as it seems, it\u2019s likely the true impacts would be worse, according to Fletcher\u2019s statements. He explained that the modeling done for `Ewa Beach does not reflect real-life conditions. Because of time constrains, he said, his team has been forced to model waves as if they are running up onto the shore in a flume, every 20 meters, rather than refracting off of each other and the environment. Fletcher said this approach has likely led to an underestimate of the threat of wave inundation.<\/p>\n
He also explained that the model being used incorporates sea level rise projections from the worst-case scenario in the Intergovernmental Panel on Climate Change\u2019s most recent report, which is far more conservative than projections by many other researchers.<\/p>\n
\u201cWe might be shooting too low. Sea level may certainly be much higher,\u201d he said. \u201cLooking at the geological evidence, we know sea level rise is not going to stop at 2100.\u201d<\/p>\n
Given current temperatures, which are one degree Celsius more than those in the pre-industrial era, sea level will not stop rising until it\u2019s 10 feet above pre-industrial levels, he said, adding that if they rise \u2014 in accordance with the cap agreed to at the recent United Nations climate change conference in Paris \u2014 to two degrees above pre-industrial levels, sea level will rise for many meters above that.<\/p>\n
A recent study by SOEST researchers found that once sea level rises to certain critical elevations, flooding increases dramatically. For `Ewa Beach, the model shows that a four-foot rise in sea level \u2014 only 25 percent more than what\u2019s projected for 2100 \u2014 will lead to \u201cenormous flooding\u201d by groundwater and the ocean.<\/p>\n
\u201cIf we get to four feet, which we eventually will, it\u2019s a catastrophic situation,\u201d he said.<\/p>\n
SOEST has done the same kind of modeling for several other communities on O`ahu. Over the next year or so, Courtney said, Tetra Tech will eventually be doing similar analyses for every island to \u201cprovide benchmark information to start thinking about these challenges ahead.\u201d<\/p>\n
\u201cWe\u2019re an island state. We may not be able to move our airport. We may have to find ways to protect critical infrastructure with hardening structures even though we know that has some adverse effects,\u201d she said.<\/p>\n
With regard to structures not yet built, \u201cwe need to think about how to discourage development in high risk areas,\u201d she said, posing the question: \u201cDo we need property disclosures to help us say, \u2018There are certain hazards on this property\u2019?\u201d And when it comes to expensive public projects, \u201chow do we ensure these projects are considering sea level rise?\u201d she asked.<\/p>\n
Ensuring government planning documents include the latest climate science is a start. Last year, the former head of Honolulu\u2019s Department of Environmental Services lamented at an engineering workshop that the county\u2019s planning documents so far have not taken climate change or sea level rise into account. Courtney noted that Kaua`i county, at least, has finally decided to incorporate sea level rise and climate change into its general plan update.<\/p>\n
\u2014 Teresa Dawson<\/i><\/b><\/p>\n","protected":false},"excerpt":{"rendered":"
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