New PROTECT publication

Chronic Flooding Events Due to Sea-Level Rise in French Guiana

Flooding at high-tide are projected to become more frequent as sea levels are rising. Although not devastating, they create a nuisance to people and infrastructure. To date, they have been mostly documented in areas where, in addition to sea-level rise, oceanic variability and geological processes triggering land subsidence take place.

In this new study, we examined a flooding event that happened in Cayenne (French Guiana) under calm weather conditions on 16 October 2020 (see Figure 1, left). We collected testimonies and physical evidence related to this event and analysed its underlying physical drivers by combining relative sea level (RSL) and daily maximum water levels with topography data obtained from field surveys and digital elevation models. We conclude that this event would have been unlikely without sea-level rise induced by climate change (Figure 1, right). 

Figure 1: Inundation photograph taken on the 16th of October 2020 at 16:00 (UTC-3) on the Serge Brown street (left) and related exceedance probability assessment of the 1d/year water level in Cayenne (right).

In the future, we show that many low-lying areas along the French Guiana will experience increasing chronic flooding. The frequency and severity of these events will strongly depend on future climate change and therefore future greenhouse gas emissions (Figure 2). Furthermore, the initiation of an ice-sheet collapse in Antarctica would result in a rapid increase in the number of flooding events after 2050. As concerns are growing regarding the economic impacts and adaptation challenges of high-tide chronic events across the world, our study provides new evidence that this early impact of sea-level rise is emerging now. 

Figure 2: Number of flood days (in days/year) exceeding the 1 day/year water levels of the 2020 event in Cayenne, French Guiana (used as a reference)

This work was performed within the frame of the GuyaClimat project and was supported by the H2020-Protect project.

Reference : Thiéblemont, R., Le Cozannet, G., D’Anna, M. et al. Chronic flooding events due to sea-level rise in French Guiana. Sci Rep 13, 21695 (2023). 

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