# Heatwave Predisposition in Dakar: Mapping and Identification of Priority Intervention Areas through Multi-Criteria Spatial Analysis

Malé Kital, Romain Courault, Marianne Cohen

► To cite this version:

Malé Kital, Romain Courault, Marianne Cohen. Heatwave Predisposition in Dakar: Mapping and Identification of Priority Intervention Areas through Multi-Criteria Spatial Analysis. Climat et Impacts, ENS-Paris-Saclay, Nov 2024, Paris, France. hal-05265926

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Submitted on 18 Sep 2025

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Distributed under a Creative Commons Attribution 4.0 International License
Unité de Recherche de Sorbonne Université

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MÉDIATIONS

Sciences des lieux, sciences des liens

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SORBONNE
UNIVERSITÉ

CRÉATEURS DE FUTURS
DEPUIS 1257

8ème édition

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Colloque

CLIMAT ET IMPACTS

6, 7 & 8 novembre 2024

Université Paris-Saclay
ENS Paris-Saclay

# Predisposition to heat waves in Dakar: mapping and identification of priority areas of intervention by multi-criteria spatial analysis

1. Laboratoire Médiations

Maison de la recherche

28 rue Serpente 75006 Paris France

https://laboratoire-mediations.sorbonne-universite.fr

2. Université Paris 1 - Panthéon Sorbonne, UMR Ladyss

Bâtiment de recherche sud -Campus Condorcet - Aubervilliers, France

Malé KITAL

male.kital@sorbonne-universite.fr

Kital, M.,¹ Courault, R.,² & Cohen, M.¹
# Plan

I. Dakar, West African Coastal Zone: Extreme Heat and Heat Waves (HV)

II. Multi-criteria spatial analysis of heat waves susceptibility: unweighted additive overlay approach

III. Result and discussion: islands of freshness, areas of low, moderate and high sensitivity to heat waves

Conclusion and outlook

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Laboratoire MEDIATIONS
Unité de Recherche de Sorbonne Université
# Background and objectives of the research1/2

**Background:** PhD research on Nature-based solutions (NBS) to address societal challenges in Dakar, including heatwaves.

## Extreme heat and heat waves in West Africa between 1961-2014

* Increase in very hot days > 35°C: + 1 to + 9 days/decade

* Increase in tropical nights > 20°C: +4 to +13 nights/decade

* Reduction of cold nights

## Extreme heat and heat waves projected in West Africa

* Potentially lethal heat days:

50-150 days/year (warming 1.6°C);

100-250 days/year (warming 2.5°C).

* Marked increases in coastal areas.

* «With increasing urbanization, cities such as Lagos, Niamey, Kano and **Dakar** are particularly exposed» IPCC Regional Fact Sheet (AR6) by (New et al., 2022)

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Laboratoire MEDIATIONS
Unité de Recherche de Sorbonne Université
# I. Background and objectives of the research 2/2

## Objectives

1. Mapping the predisposition to heat waves in the Dakar region

* Produce a tool for identifying the areas most sensitive to heat waves.

* an intermediary object for the co-construction of nature-based solutions.

2. Identifying priority areas for nature-based solutions

* Identify ecosystems to be protected or restored.

* Identify areas to be renatured for urban cooling.

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Materials and Methods 1/2

Dakar Peninsula

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❖ **Location:** Westernmost part of the African continent.

**Latitudes:** 14°53' and 14°35' N

**Longitudes:** 17° 10' and 17°32'

**Area:** 550 km² = 0.28% of the area of Senegalese territory

**3,896,764 inhabitants in 2023 = 21.6% of the national population**

❖ **Urbanization and environment**

Increased demographic pressure, urban sprawl, degradation of ecosystems and the living environment of populations

❖ **Effects of climate change**

Floods, erosion, rising temperatures, heat waves

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# Materials and Methods 2/2

## Unweighted additive overlay « UAO » Approach

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* Choice of analysis criteria
  (Singh, 2023) &
  (Jabbar et al., 2023)

* Standardisation of criteria

* Unweighted additive overlay

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Result 1/5

Standardized criteria

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Urban heat islands

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humidex

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Emissivity

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albédo

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wind speed

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L ULC

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# Result 2/5

## Heatwave Sensitivity Map

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The cartographic result
highlights:

* ✓ Islands of freshness,

* ✓ areas of low, moderate, high sensitivity to (HV).

This zoning can be explained by land use and land cover, and by oceanic and continental factors.

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Laboratoire MEDIATIONS
Unité de Recherche de Sorbonne Université
# Result 3/6

## Islands of freshness to be protected or restored

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* **Priority ecosystems for protection**
(wetlands, dense vegetation cover, seafront, which offer essential islands of freshness)

* **Ecosystems to be restored**
Degraded cool areas, with the potential to become islands of freshness again, but requiring restoration efforts to maximize their climate efficiency.

**Exemples** : Mbao forest, the strip of casuarinas

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# Result 4/5

## High HV Sensitivity Areas

Areas that are highly susceptible to heat waves due to a strong urban heat island effect.

* Most distinguished areas are

* ✓ Industrial sites,

* ✓ Mbeubeusse landfill

* ✓

* ✓ Large asphalt surfaces((LSS Airport and VDN3))

* ✓ The south-east of Dakar has a low albedo which can be explained by the geological substrate (lithosols and vertic soils)

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# Result 5/5

## Areas of moderate sensitivity (Areas to be renatured)

* **Urban area:** Working-class neighbourhoods characterised by a high density of buildings and the absence of vegetation

* **Peri-urban area:** Working-class suburbs, marked by informal settlements and lack of vegetation. It is moderately sensitive to heat waves, despite the effect of oceanity

* **Expansion zone:** An area with little or no urbanization, close to the mainland and subject to the effect of continentality.

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# Discussion 1/1

❖ **Methodological approach: unweighted additive overlay**

✓ an effective approach to mapping predisposition to heatwaves (Singh, 2023),

✓ but it does not take into account the varying degrees of influence that the analysis criteria can have on temperatures.

❖ **Practical interest of the result**

✓ This result indicates that targeted interventions, such as increasing green spaces, using high reflectivity building materials will effectively reduce local temperatures.

✓ Priority areas for these interventions include densely populated neighbourhoods with few green spaces and inland neighbourhoods affected by continentality.

✓ The map also shows that urban expansion inland, in particular the creation of new towns, must imperatively integrate fresh grids and avoid the lithosol zone.

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Conclusion and outlook

The unweighted additive superimposition of criteria (urban heat islands, humidex index, emissivity, albedo, wind speed, land use) made it possible to visualize the relationship between urban land use planning and the predisposition to heat waves in the Dakar region.

This cartographic result is:

* a tool for identifying the areas most sensitive to heat waves,

* an intermediary object for the co-construction of solutions to meet the challenge of extreme heat episodes in Dakar

These priority areas will be analysed in detail to identify nature-based solutions that take
into account local realities.

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Bibliography

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Dubé-Poirier, C.-É. (2023, janvier). *Caractéristiques spatio-temporelles des vagues de chaleur estivales dans le bassin versant de la rivière des Outaouais, Ontario-Québec, Canada* [Mémoire accepté]. Université du Québec à Montréal. https://archipel.uqam.ca/16356/

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Thank you for your attention!

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Laboratoire MEDIATIONS
Unité de Recherche de Sorbonne Université