Fernando Alcoforado*
This article aims to present the impact of floods on Salvador from 2030 onwards resulting from the rise in sea levels as a result of global warming and climate change that are already happening on our planet, as well as to propose solutions to mitigate or avoid their catastrophic consequences. Sea level rise is one of the best-known threats resulting from global warming and climate change. While humanity pollutes the atmosphere with greenhouse gases, the planet warms up. Moreover, in doing so, ice sheets and glaciers melt and warm seawater expands, increasing the volume of water in the world’s oceans. Floods from coastal regions can damage the infrastructure of cities and plantations in rural areas and require the permanent displacement of populations residing in coastal regions. Globally, rising sea levels could have a significant impact in the coming years. Potential impacts of sea level rise include flooding, erosion of coastal regions and submergence of flat regions along the mainland coast and on islands. Over the 21st century, global sea levels are projected to rise by between about 61 cm and 2.13 m by 2030, and possibly as much as 7 meters by 2100, if nothing is done to avoid them. Projecting where and when this increase could translate into an increase in partial and permanent flooding is important for planning coastal regions and cities. Projecting flood risk involves not only estimating future sea level rise, but also comparing it to land strip elevations.
A new digital model, CoastalDEM, was used to identify flood areas on the planet. It’s Climate Central’s high-precision digital elevation model for coastal areas that reduces average errors in NASA’s widely used SRTM DEM to nearly zero and reveals three times the flood threats. CoastalDEM shows that many of the world’s coastal regions are at very low levels and that rising sea levels could affect hundreds of millions of people in the coming decades more than previously thought. Based on sea-level projections for 2050, the land that is currently home to 300 million people will be below the elevation of an average annual coastal flood. By 2100, the land that is now home to 200 million people could be permanently below the high tide line. Adaptive measures, such as building dikes and other defenses or relocating to higher ground, can alleviate these threats. In fact, based on CoastalDEM, about 110 million people currently live on land below the high tide line. This population is almost certainly protected to some degree by existing coastal defenses that may or may not be adequate for future sea levels. Despite these existing defenses, increasing ocean flooding, permanent submergence and coastal defense costs are likely to have profound humanitarian, economic and political consequences. This will happen not only in the distant future, but also during the lives of most people alive today.
Some maps show the regions of the city of Salvador, Bahia, and its metropolitan region that may be submerged from 2030 onwards, which were prepared based on CoastalDEM, a tool created by Climate Central, which shows the regions that may be below the level of sea in a few years [Martins, Bruna. Mapa mostra áreas de Salvador submersas em 2030 (Map shows submerged areas of Salvador in 2030). Available on the website <https://casavogue.globo.com/um-so-planeta/noticia/2021/08/mapa-que-mostra-areas-de-salvador-submersas-em-2030-viraliza-nas-redes-sociais.html> published in 18/08/2021]. Floodable areas are colored red on maps. Areas of Salvador and the metropolitan region, such as the beaches of Boa Viagem (Salvador), Buraquinho (Lauro de Freitas) and Busca Vida (Camaçari) will be flooded, as well as Ilha da Maré, which appears completely submerged on the map.
Map 1- Floodable areas of the Comércio and Cidade Baixa regions
Map 2- Floodable areas in the Joanes River basin and estuary
Map 3- Floodable areas in the Bay of Aratu, Port of Aratu and Ilha da Maré
Note: Ilha da Maré, on the left, appears completely submerged
Map 4- Floodable areas in Jauá and Arembepe on the north coast of Bahia
Faced with these threats, what can be done to face the rise in sea level? The First Street Foundation that published the article Solving for Sea Level Rise, available on the website <https://medium.com/firststreet/solving-for-sea-level-rise-b95600751525>, offers answers with proposed solutions like those described below:
Solution 1: Building seawalls
One solution that cities employ to reduce tidal and storm surges is to build seawalls. These barriers are usually built at a height of 1.52 meters to 1.83 meters above sea level. When seawalls or breakwaters age or are damaged by constant exposure to salt water or the impact of waves, they need to be replaced. They also need to be replaced or built higher as sea levels continue to rise.
Solution 2: Using beaches and dunes as barriers
Similar to seawalls, beaches and dunes can act as a natural wall and reduce the impact of ocean waves and storms. The larger the beach or the larger the dune, the more water can be prevented from reaching houses and roads. City rulers can add sand to enlarge beaches or to prevent them from eroding. Using this type of natural infrastructure can protect cities from flooding while maintaining beaches for the community to enjoy.
Solution 3: Raising the road level
Raising roads above sea level can help drain water and reduce tidal flooding. To ensure that higher roads do not channel floodwater to homes and shops at lower elevations, cities rulers often pump storm water to remove this excess water.
Solution 4: Pumping rainwater
With higher seas, water doesn’t flow into the ocean as easily. Drainage systems are designed to funnel excess rainwater from the streets and drain it into the sea, but the pressure of rising sea levels and high tides can push too much water into these pipes, causing water to drain leak into the streets. Pumps can speed up the process of removing water from the streets, sucking in flood water and releasing it back into the sea.
Solution 5: Updating sewer systems
Floods can disrupt sewage systems and, in particular, threaten septic tanks. As salt water is corrosive, it can damage tanks and cause sewage to be expelled, creating health risks for the population. Cities rulers can upgrade sewer systems so that rainwater does not seep into the pipeline and upgrade septic tanks or replace them with sewer lines.
Solution 6: Creation of natural infrastructure
Coastal communities can restore natural infrastructure, which can act as a buffer against coastal storms and floods. Natural structures such as barrier islands, coral reefs, mangroves, sea grasses and salt marshes can function alone or in conjunction with built-in infrastructure such as breakwaters to absorb the storm surge. These projects are often cost-effective, can improve the natural environment for the community, and save important habitats.
Solution 7: Decreasing land sinking
Cities can reduce land sinking by limiting groundwater pumping and initiating pilot projects to reverse land sinking by filling empty space in places where groundwater has been pumped.
Solution 8: Managed population relocation
This solution is adopted in some coastal areas that are being lost to storms, sea level rise, erosion and land sinking. While communities are implementing many of the solutions available to help prevent land loss, relocation of populations should be considered in extreme cases. This may not be the best option for all coastal communities facing the imminent threat of sea level rise, but for some it is the best solution for keeping residents safe.
In addition to the above-described local solutions, the measures advocated by the Paris Agreement on the climate should be adopted simultaneously to reduce the global emission of greenhouse gases (carbon dioxide, nitrous oxide, among others) to prevent global warming of more than 2 degrees Celsius (°C) by the end of the 21st century. In this sense, it is imperative to reduce global concentrations of carbon dioxide (and equivalents) to 450 ppm (parts per million). In addition, it is necessary to globally reduce the amount of nitrous oxide (a gas that reaches the ozone layer and increases global warming) released into the atmosphere, which could more than double by the middle of the 21st century. For this, global emissions will have to be reduced below 1990 levels. Two strategies are essential for the immediate reduction of the emission of greenhouse gases, which are the realization of changes in the energy matrix and in the transport matrix with the abandonment of the use of fossil fuels and their replacement by renewable sources of clean energy (solar, wind, biomass, hydrogen, among others). To succeed in achieving these goals, it is important that national governments act in a coordinated way to combat climate change to make the Paris Agreement effective.
* Fernando Alcoforado, 81, awarded the medal of Engineering Merit of the CONFEA / CREA System, member of the Bahia Academy of Education, engineer and doctor in Territorial Planning and Regional Development by the University of Barcelona, university professor and consultant in the areas of strategic planning, business planning, regional planning and planning of energy systems, is author of the books Globalização (Editora Nobel, São Paulo, 1997), De Collor a FHC- O Brasil e a Nova (Des)ordem Mundial (Editora Nobel, São Paulo, 1998), Um Projeto para o Brasil (Editora Nobel, São Paulo, 2000), Os condicionantes do desenvolvimento do Estado da Bahia (Tese de doutorado. Universidade de Barcelona,http://www.tesisenred.net/handle/10803/1944, 2003), Globalização e Desenvolvimento (Editora Nobel, São Paulo, 2006), Bahia- Desenvolvimento do Século XVI ao Século XX e Objetivos Estratégicos na Era Contemporânea (EGBA, Salvador, 2008), The Necessary Conditions of the Economic and Social Development- The Case of the State of Bahia (VDM Verlag Dr. Müller Aktiengesellschaft & Co. KG, Saarbrücken, Germany, 2010), Aquecimento Global e Catástrofe Planetária (Viena- Editora e Gráfica, Santa Cruz do Rio Pardo, São Paulo, 2010), Amazônia Sustentável- Para o progresso do Brasil e combate ao aquecimento global (Viena- Editora e Gráfica, Santa Cruz do Rio Pardo, São Paulo, 2011), Os Fatores Condicionantes do Desenvolvimento Econômico e Social (Editora CRV, Curitiba, 2012), Energia no Mundo e no Brasil- Energia e Mudança Climática Catastrófica no Século XXI (Editora CRV, Curitiba, 2015), As Grandes Revoluções Científicas, Econômicas e Sociais que Mudaram o Mundo (Editora CRV, Curitiba, 2016), A Invenção de um novo Brasil (Editora CRV, Curitiba, 2017), Esquerda x Direita e a sua convergência (Associação Baiana de Imprensa, Salvador, 2018), Como inventar o futuro para mudar o mundo (Editora CRV, Curitiba, 2019) and A humanidade ameaçada e as estratégias para sua sobrevivência (Editora Dialética, São Paulo, 2021) .
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