But Does It Float?
An introduction into my research project for the Design by Data Advanced Master in Computational Design, Digital Manufacturing and Building Technologies at Ecole des Ponts ParisTech.
This, my inaugural Medium post, certainly won’t be as visually stimulating or nuanced as its namesake; But Does it Float (an ongoing image-based conversation between Superfamous Studios’ Folkert Gorter, Atley G. Kasky, and Will Schofield occurring online). But I hope that by the close of this piece you feel that the rationale behind my research project has buoyancy, a sense of robustness and, most importantly, that the idea doesn’t sink like a stone!
Sea Level Rise
The Intergovernmental Panel on Climate Change (IPCC) (2013) present estimates for a number of different scenarios, presented as Representative Concentration Pathways (RCP). The RCPs depend on a range of different factors, including; population growth, GDP growth, energy use, land use changes, resource availability, and the pace and direction of technology.
A brief description of each of the IPCC RCPs is as follows:
- RCP2.6: Assumes that global annual greenhouse gases (GHG) peak between 2010–2020, with emissions declining substantially thereafter;
- RCP4.5: Assumes that GHG emissions peak at 2040, then decline;
- RCP6.0: Assumes that GHG emissions peak at 2080, then decline;
- RCP8.5: Assumes that GHG emissions continue to rise throughout the 21st century.
The shaded region on the above chart displays the medium confidence range for RCP2.6 and 8.5. The medium range is shown to have larger estimates for the global mean sea level rise, especially later in the century, when compared to the likely ranges presented to the right of the chart. The IPCC (2013) states that there currently is insufficient evidence to evaluate the probability of specific levels above the likely range. Based on current understanding, only the collapse of marine-based sectors of the West Antarctic Ice Sheet (WAIS), if initiated, could cause global mean sea level (GMSL) to rise substantially above the likely range during the 21st century. There is a lack of consensus on the probability for such a collapse, and the potential additional contribution to GMSL rise cannot be precisely quantified.
Rignot, et al. (2014) and Joughin, et al. (2014), released subsequent to IPCC (2013), strongly suggest that the WAIS has already entered the early stages of collapse, but state that the contribution of WAIS to GMSL cannot yet be determined with sufficient confidence.
Therefore, a conservative SLR value of 1.15 m for 2100 compares to the values presented for this time period by Mather & Stretch (2012) for Germany (1 m), the Netherlands (1.1 m) and California (1.4 m).
Higher Water Levels — Additional Components
At least five processes can be involved in altering water levels during storms:
- The atmospheric pressure effect — open ocean water levels will rise in regions of low atmospheric pressure and fall in regions of high pressure.
- The direct wind effect — the ‘wind set-up’ is the tendency for water levels to increase due to strong surface winds at the downwind direction.
- The effect of the Earth’s rotation — the Coriolis effect can amplify storm surge water levels.
- The effect of waves near the shore — waves can result in significant transport when they exit deep water, propagate in the nearshore. Waves are powered by the wind.
- The rainfall effect — this effect is more related to estuaries, and believed to have less of an impact in this project.
Research, such as that undertaken by Theron & Rossouw (2008) for South Africa, is indicating that average wind velocity is expecting to increase due to climate change.
Wave height (in a fully developed state) is proportional to the square of the wind stress factor (UA). UA is related to the wind speed (U) according to (US Army, Corps of Engineers 1984):
Thus, a 10% increase in wind speed, means a 12% increase in wind stress and 26% increase in wave height. Therefore, this component will provide an additional increase to future storm surge water levels.
Small Island Developing States
Small Island Developing States, or SIDS, such as the Maldives (pictured), are some of the most vulnerable regions, and populations, to climate change and sea level rise, as they’re mostly low-lying and are located in regions where they’ll be more susceptible to extreme weather events.
“The Maldives is one of the small states. We are not in a position to change the course of events in the world. But what you do or do not do here will greatly influence the fate of my people. It can also change the course of world history.” — Statement by H.E. Maumoon Abdul Gayoom (Maldives) 4 December 1997, Kyoto, Japan.
As you can see in the figure below, many of the SIDS are located within the tropics.
This excerpt from the Washington Post highlights the startling predicament that the Maldives, and other SIDS face:
Take, for instance, the city of Male, the capital of the Maldives. According to a 2001 report from the U.N.’s Intergovernmental Panel on Climate Change, with a 90 centimeter rise in seas, 85 percent of it could be “inundated,” barring costly adaptation measures. (The island has built considerable seawalls, however.) Indeed, the highest elevation in the small island chain, which is home to some 400,000 people but in total area not much bigger than D.C., is just 2.4 meters above present sea level.
And the Maldives aren’t even the most vulnerable of island nations. Also in 2001, the IPCC noted that just 80 centimeters of sea level rise would flood two-thirds of Kiribati and the Marshall Islands.
Forty-three of the world’s smallest island and low-lying coastal countries, representing the most susceptible States to change in climate, have previously forged a coalition called the Alliance of Small Island States (AOSIS) (most, but not all are SIDS too). While AOSIS represents more than one quarter of the world’s countries, together they account for less than one per cent of global carbon emissions (UN Chronicle).
There have been several reports (e.g. 1 & 2) that some SIDS members, those with the lowest land heights, are in discussions with larger countries, such as India or Australia, as potential places to relocate their populations given worsening effects of sea level rise and climate change. Recent reports have emerged that the Maldives are even looking at selling an entire atoll to Saudi Arabia.
Therefore, the SIDS that I’m most interested in for my research project are low-lying, predominately sand islands that are surrounded by a coral atoll. This is an affected population of approximately 20 million people.
Nature’s Coastal Protection
Of course, these islands endured centuries of storm, wave and ocean current (hydrodynamic) action — yet they’ve continued to exist.
This is largely due to the natural coastal protection offered by the barrier coral reef that encircles the island and potentially assisted by plantations of mangroves, which are very effective in trapping sediment.
This short video of a physical model demonstrates how mangroves reduce wave forces:
As simply demonstrated in the figure below (derived from this study), coral reefs are extremely effective in reducing wave energy — able to “reduce total wave energy by an average of 97%”.
Here are some basics on wave breaking thanks to the good ol’ BBC:
Therefore, wave breaking is a factor of the wave length, wave height and water depth. Simplistically, shallower water depths initiate wave breaking in smaller waver heights. As deep water waves interact with a coral reef, the water depth reduces quickly (for example; from a depth of 60 m to 1 m in 5–10 m of lateral distance), and the waves break abruptly.
With more rapidly rising water levels due to climate change, the water level above the barrier reef is increasing faster than the reef can grow, which allows for larger wave heights to propagate over the reef and run up on the island’s coastline. This can lead to increased shoreline erosion and inundation during large storm or swell events.
The effectiveness of the world’s coral reefs are also been affected by degradation due to ocean acidification, increasing sea water temperatures and particular fishing techniques.
A lack of natural coastal protection will mean that the SIDS will experience increased erosion. Constantly addressing erosion issues will place substantial financial burden on these developing nations.
Research Project Idea
Therefore, my project will seek to develop a floating (likely modular) coastal protection structure that will be placed inside the existing coral reef. The structure will provide protection from waves with heights that no longer break on the barrier reef given the increased water levels experienced by the islands due to sea level rise and climate change (large waves will continue to break on the existing reef).
Landward of the external coastal protection units will be floating platforms that will form space for habitation for the island population that may have to be relocated due to the rising water levels. Therefore, the affected population would only move to the floating platforms in the lagoon adjacent to the island, rather than being forced to shift to more distant countries. This would be key in maintaining personal, traditional and cultural ties to the island — the importance of which, is raised in the following piece on the plight of Tuvaluans:
As more and more Tuvaluans migrate to New Zealand and Australia, individual representatives of the culture who would normally pass on the traditions of Tuvalu assimilate into foreign lifestyles. Eventually, as water completely claims the land, Tuvalu will completely lose its sovereignty, forcing Tuvaluans to follow the laws and customs of other nations.
The reduction in quality of health and elimination of Tuvalu sovereignty will place unprecedented stress on the culture of the 10,782 residents, most of whom claim Polynesian heritage with a minority born from Micronesian roots. Despite the peaceful nature of Tuvaluans, competition for increasingly scare resources, exposure to intensifying natural disasters and absorption into societies more violent than their own will likely change the culture of Tuvalu on a permanent basis.
I aim to achieve a computationally or data-driven system that can rapidly present an overview of a possible structure, as well as its location and size, when provided the bathymetry and topography of the island, the proposed sea level rise scenario height and the number of people living on the island.
The location of structure will be determined in response to the dominant wind and wave directions occurring at the island. The historical conditions will be extracted from the National Centers of Environmental Prediction (NCEP) WaveWatchIII database.
The following figure provides an example of the seasonal wave direction distribution for the KwaZulu-Natal coastline, South Africa. Therefore, the hypothetical structure would be placed to shield from the waves that come from the south-south-east.
The plan size of the floating structure is to be determined by applying the sea level rise height scenario (entered by the user) to the population distribution of the island. For example, if the sea level rise height is 2.5 m height, then the script must calculate the population of people that live below that height (example show below) and create the correct number of floating platform modules to suitably house the people on the lagoon (in the lee of the seaward protection components).
Utilising the Rhino 3D plug-in, Grasshopper, further constraints will govern the location of the floating structures.
In summary, climate change and sea level rise is having an increasingly detrimental effect on the many millions of people that inhabit SIDS. It would be more beneficial if these people could maintain links to their traditional lands, instead of relocating due to climate change.
Innovative design solutions are required to address the situation experienced by the SIDS, especially those that are a low-lying. The application of computational design techniques can reduce the time required to explore design solutions, produce prototypes and optimise the proposed solution given the location specific environmental conditions.
A floating coastal protection and habitation structure could assist in addressing living conditions for the SIDS populations in the near- to long-term future (100 years).
A robust solution would allow the input of site specific datasets (metocean, bathymetric, topographic and demographic data) and output an optimised solution for a sea level rise scenario given by the user.
But does the idea float?
