Associated Programme on Flood Management (APFM),
World Meteorological Organization (WMO)
Imagine a region with 2 million inhabitants, a port that manages 15% of the national maritime harbor handling rate, considerable oil and gas offshore reserves, and a flourishing tourist industry. Now, add to this picture climate changes influencing tidal level, currents, and waves, inducing extreme weather events, with their list of backlash on coastal erosion, land flooding, survival of marine ecosystems: could you conceive the effects of all this on our prosperous coastal area?
This is exactly the kind of situation that the Santos Harbor Metropolitan Area risks to face in the next years (Figure 1). Different studies have confirmed that coastal locations are supposed to be particularly vulnerable to the effects of climate change. Especially those regions where infrastructures and sensitive values are concentrate dare expected to suffer more significant losses.
Figure 1- Map of the São Paulo state southern coastal area where is located Santos Harbor.
The challenge stands clear and sharp in front of policy makers: to spare the harbor and its surroundings from this gloomy scenario, the imperative is to minimize risks. But to do so, they need the most possible complete picture of the processes triggered by climate change and their impacts on the coasts.
Here is where geospatial sciences come to the aid of Santos port. In a recent investigation, a group of researchers from the universities of Sao Paulo (Brazil) and Turin (Italy) and the Aeronautic Technology Institute of San Jose dos Campos (Brazil) have determined an increase in the wave significant height and in the wave peak period, as well as in the frequency of storm surges events during the last decade in the coastal area around Santos. The conclusion originates from an innovative analysis of a long-term wave database (1957-2002) created through the comparison between wave data modeled on “deep water model” (ERA-40 Wave model – ECMWF) and another set of data measured by a coastal buoy from 1982 to 1984. Through a near-shore wave model (MIKE21), the figures obtained from the comparison were applied to the original scenarios, so as to generate calibration coefficients. Translation for dummies: you take a set of data produced through a model analyzing “deep water”, contrast it with real data measured on the ground (or better, on the sea in this case) in “shallow water” and adjust the achieved results by means of another model merging the two dimensions (deep and shallow), Figure 2.
Figure 2-Detailed flooding areas of Santos Harbor Inner Port for a relative sea level rise of 1.5 m (greenlines are future levels of low water and redlines are high water ones).
Nonetheless, you will not be able to do this, if you do not know the bathymetry (i.e. the configuration of underwater terrain expressed as depth below sea level) of the area you are going to examine. The research group chose to approach this step by elaborating a mesh showing the changes in the seabed with the help of ESRI ArcGIS and DHI MIKE Zero softwares. While the first was employed to geo-reference eight nautical charts and build a suitable geographic GIS model, the latter was processed to actually construct the mesh.
Good methodology, sound results. But how the passage from a more solid database to policy making is then made may not be so clear. The missing link lies in the use of the results obtained to forecast the possible effects of climate change on the characteristics of waves and, consequently, their impacts on the coastal area. Integrating the outcomes of this study with previous investigations, the research group estimated a sea level rise and subsidence between 50 and 100 cm/century in the next decades, resulting in a flooding of around 50% of the present Santos Estuary mangroves and around 100 m of the beaches in 2100. Not only: overlapping 29 regional maps of the Sao Paulo Cartographical and Geographical Institute, a digital terrain map was produced displaying the areas likely to be flooded according to four different scenarios of the sea level rise. To complete the picture, the overall impacts of climate change are expected to affect around 100.000 inhabitants and cause more than 7 billion US$ damages in the Santos Harbor Metropolitan Area by 2100 (Figure 3).
Figure 3-Flooding areas of SHMA for different rates of mean sea level rise from present mean sea level (PMSL) and considering an additional storm surge extreme event with 1.0 m rising over PMSL
The outlined scenario represents an incredibly precious resource for managers and urban planners to design adaptation policies in a medium and long term perspective. Based on the predictions formulated in the research, a strategic plan focusing on the navigation and coastal defenses for Sao Paulo State coastline has taken shape. It includes a broad range of structural and non-structural measures belonging to different fields of action (protection, resistance and resiliency, system management, impact management, information and coordination), such as wetlands restoration, jetties, seawall, dikes construction, focus investments on lower-risk assets, shifting of operations to less exposed areas, development of partnership between ports and their host regions, and information on best practice responses, just to name few.
Whether or not the package of actions will work will become evident in the next years. Nevertheless, researchers underlined that the intervention plan might need further adjustments throughout the course of its implementation, considering that unforeseen effects of climate changes could materialize and interfere with the scheduled measures. In the meanwhile, science may also progress, refining or producing new tools to support urban and coastal planning. All in all, when dealing with natural events, the aphorism of the Greek philosopher and scientist Aristotle is more than ever topical: “It is very probable that the improbable will happen”.
Alfredini, P., Arasaki, E., Pezzoli, A., Arcorace, M., Cristofori, E., de Sousa, W.C.Jr., “Exposure of Santos Harbor Metropolitan Area (Brazil) to Wave and Storm Surge Climate Changes”, Water Quality, Exposure and Health, June 2014, Volume 6, Issue 1-2, pp 73-88.