Virginia Beach is a resort city with around 500 000 inhabitants. The economy is heavily reliant on its near-sea level installations, which are extremely vulnerable to sea level rise. Many homes are also exposed, driving officials to consider expensive flood protection plans, but will they be enough for the worst-case scenario?
Earth.Org has mapped coastal flooding at Virginia Beach under a high emissions scenario to help visualize the risk it is facing.
Hundreds of houses and many roads are frequently flooded in Virginia Beach. In the last few years, tides have been noticeably higher, and officials are taking mitigation measures, passing a flood control program to safeguard this seaside community.
The plan, dubbed Sea Level Wise, consists of developing engineered defenses, adapting structures, natural mitigation, and preparing the communities at risk. It is a multi-billion dollar project that will feature purchasing structures at risk and rebuilding in safer locations, new requirements for building ground floor elevation, and seawalls.
There is a glaring issue. Critical infrastructure like hospitals will prepare for about a meter sea level rise, while non-critical building for half a meter. Unfortunately, a recent paper published in Nature estimates that, under high emissions scenarios, global sea levels could rise by an average of 1 to 2 meters by 2100.
We all hope that the worst-case scenario does not materialize, and it is difficult to ask communities to invest accordingly, but recent news on the unexpectedly rapid ice loss of the Antarctic ice sheet is not reassuring. Earth.Org has modelled what flooding could look like in Virginia Beach by 2100 if we continue on our current course.
Sea Level Rise Methodology
Global mean sea level is projected to rise by 2m at the end of this century. However, in order to determine local sea level rise (SLR), one has to take into account local coastal flood levels which could be 2.8m above Mean Higher-High Water (MHHW) at extreme forecasts. These local levels bring variability to the projected SLR from 1m to 6.5m (eg. Rio vs Kolkata).
The SLR scenarios used in this study are based on the forecasts from Climate Central ? Coastal Risk Screening Tool with the following parameters:
- Sea level Projection Source
- Coastal Flood Level
- Pollution Scenario
Sea level Projection Source:
From two highly cited journals by Kopp et al., estimating SLR mainly due to ocean thermal expansion and ice melt. The mid-range scenario projected 0.5-1.2m of SLR based on different representative concentration pathways (RCP) defined by the IPCC. While the pessimistic scenario added more mechanisms of ice-sheet melting, estimating SLR at 1m-2.5m in 2100, with a projection of 10m SLR at 2300.
More frequent coastal flooding is a direct impact of sea-level rise. Based on the Global tides and surge reanalysis by Muis et al., (2016), it is estimated that the extreme coastal water level could be from 0.2 – 2.8m over the mean level. While in extreme cases like China and the Netherlands it could experience 5-10m of extreme sea levels. Here, the coastal local flood level is added on top of the projected SLR.
Allows choosing the RCP, the greenhouse gas concentration trajectory defined by the IPCC. The mild level is based on RCP4.5, of 2°C temperature rise; while the Extreme level is based on RCP 8.5, of 4°C temperature rise.
Applies to the baseline SLR, defined in the “Sea level projection” section, upon which we add flooding. “Mild” refers to the mid-range scenario of 0.5-1.2m, and “extreme” to the pessimistic scenario of 1-2.5m. We used the high-end value of each scenario (mild = 1m; extreme = 2.5m).
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Kulp, Scott A., and Benjamin H. Strauss. “New elevation data triple estimates of global vulnerability to sea-level rise and coastal flooding.” Nature communications 10.1 (2019): 1-12.
Florczyk, A. J., Corbane, C., Ehrlich, D., Freire, S., Kemper, T., Maffenini, L., Melchiorri, M., Politis, P., Schiavina, M., Sabo, F. & Zanchetta, L. (2019). GHSL Data Package 2019 Public Release.
Kopp, R. E., DeConto, R. M., Bader, D. A., Hay, C. C., Horton, R. M., Kulp, S., Oppenheimer, M., Pollard, D. & Strauss, B. H. (2017). Evolving Understanding of Antarctic Ice-Sheet Physics and Ambiguity in Probabilistic Sea-Level Projections. Earth?s Future, 5(12), 1217?1233.
Kopp, R. E., Horton, R. M., Little, C. M., Mitrovica, J. X., Oppenheimer, M., Rasmussen, D. J., Strauss, B. H. & Tebaldi, C. (2014). Probabilistic 21st and 22nd Century Sea-Level Projections at a Global Network of Tide-Gauge Sites. Earth?s Future, 2(8), 383?406.
Kulp, S. A. & Strauss, B. H. (2019). New Elevation Data Triple Estimates of Global Vulnerability to Sea-Level Rise and Coastal Flooding. Nature Communications, 10(1), 4844. Retrieved June 21, 2020, from http://www.nature.com/articles/s41467-019-12808-z
Muis, S., Verlaan, M., Winsemius, H. C., Aerts, J. C. J. H. & Ward, P. J. (2016). A Global Reanalysis of Storm Surges and Extreme Sea Levels. Nature Communications, 7.