Scientific stopovers on the coastline of the Indian Ocean 3/4 - Coastlines under strict scrutiny

Coral sampling by the Line intercept transect method © IRD - Pascale Chabanet

In Reunion, IRD scientists and their partners have set up several projects to closely follow the evolution of the region's coastlines.

Go to previous stop of the journey.

The coastal ecosystems of the southwest Indian Ocean plays a crucial role in the protection of the coastline and must in turn be protected, in particular through careful year-round monitoring.

Pascale Chabanet, from IRD, contributes to the GCRMN global project to monitor the health of coral reefs. She regularly dives around the island with her colleagues, equipped with underwater pads, black pencils and a 50-meter tape measure.

A complete local survey

After delicately putting the tape on the reef, the researcher-divers write down all the corals and algae types they can see around the tape, as well as their size. Others are responsible for listing the number and size of all the fish they can see in a 5-metre wide corridor along the measuring tape.

Pascale explains: “We have used this standardized method of observing reefs for years around the world. Thanks to the data collected, we are able to determine the health condition of reefs around the world and their evolution from one year to the next. We can also recommend, for example, management measures to regulate fishing". Other research projects complete the observations made by the GCRMN by studying the causes of these changes.

The two videos below (in French) describe the survey method used by GCRMN.

Assessing the damages of a cyclone by satellite

Let us stay in Réunion where several cyclones hit the coasts each year, like in many islands and countries bordered by the Indian Ocean. The IRD and its partners in Réunion and Madagascar use data collected through remote sensing to assess the natural and material damage they cause on the coasts.

The Remote Sensing and Geomatics Competence Centre based in Saint-Pierre de la Réunion collects satellite images of the coasts of the area, updated every five days. By comparing images taken before and after a cyclone has passed, researchers are able to estimate the impacts on urban areas, forests, coastlines and agricultural areas.

Detecting changes automatically

The scientists ultimately wish to design and deploy an automated chain for detecting changes in surface conditions following a natural disaster by remote sensing.

Once collected, this monitoring information is intended to support policy makers in the Indian Ocean in their decisions for better coastal protection.

Go to the next stop of the journey.

This paper has first been published by IRD.

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