In 2005, the Dakar metropolitan region received its highest rainfall in nearly 20 years, and widespread flooding occurred across much of the region. In Pikine, a city in suburban Dakar with nearly 1.2 million residents, the floods displaced thousands of people and cost billions of francs to clean up [1
]. Since then, approximately one-third of Pikine’s population has been regularly impacted by flooding, including people living in areas that did not previously flood [2
Floods are the most common type of natural disaster in the world and affect millions of people each year [3
]. Climate change will contribute to increases in both intensity and frequency of floods and in the damages they cause [3
]. Yet, these projected changes are complex. Many, but not all, regions will likely see more frequent floods, and the flood season may be earlier in some regions but later in others [6
]. Likewise, any projected changes cannot be explained solely by changes in precipitation, since flood characteristics are strongly dependent on the geographic context [6
]. The models used to predict future flood risk and frequency do not always find the same outcomes and do not take into account any potential mitigation measures [6
]. In fact, these projections may be overly pessimistic about human impacts and too optimistic about their reliability [10
]. Still, climate change will impact future flooding even if the magnitude is unclear.
In many countries, flood vulnerability will increase because of population growth and spatial expansion [11
]. Between 1970 and 2010, the value of assets and the population exposed to flooding increased substantially, with the largest increase in exposed population occurring in Sub-Saharan Africa [4
]. Furthermore, it is Sub-Saharan African cities that are at increasing vulnerability to flooding [12
]. They are also predicted to experience some of the most severe impacts from these disasters, partly because their residents have low levels of adaptive capacity and they often lack the resources and tools needed to prevent their homes from flooding [13
Floods disproportionately affect the poorest urban residents, especially those living in informal settlements [14
]. As Sub-Saharan Africa’s cities continue to experience rapid population growth, more people are now vulnerable to flooding and other natural hazards. This vulnerability can be attributed to a colonial history of inequality, environmental deterioration, changes in local land use, rapid urbanization, and global patterns of climate change [12
]. Rapid urbanization, in particular, affects flooding both by obstructing natural drainage patterns and by leading to large populations living on floodplains [14
]. Pikine, Senegal, is one such vulnerable city.
Flooding in Pikine has been extensively studied, particularly in terms of governance [15
], contamination of groundwater [16
], economic impacts [18
], and health concerns [2
]. Building on this previous work, this study makes three important contributions to the literature. One contribution concerns the perceived effectiveness of government interventions. Since the construction of flood catchment basin infrastructure projects, little research has investigated the impact of this infrastructure on flood control and health. This research fills an important gap in assessing how flood infrastructure may reduce households’ perceived vulnerability. A second contribution concerns the role that land tenure plays in household decisions to remain in flood-prone areas. Although Pikine began as an informal settlement, many households do have formal land rights today. The third contribution of this paper is the finding that households did not attribute health issues to environmental quality but rather drinking water, despite important environmental risk factors present across the commune.
1.1. Urban and Economic Development of Pikine
Africa’s informal settlements are sometimes described as unruly, an image that ignores their creativity and ingenuity and instead focuses on their unplanned layout [24
]. Yet, this description of unruliness presents the opportunity for their residents to be blamed for any problems. In Pikine, certainly the lack of planning contributes to flooding, but it is necessary to understand the historical context of its urban development. Suburban Pikine is intimately linked to colonial and post-colonial Dakar. Dakar was the showcase city of colonial French West Africa and served as an important economic, political, and cultural hub. Furthermore, its development was largely a story of order through displacement. Indigenous residents were first displaced from the tip of the Dakar peninsula and subsequently pushed further away to the outskirts of the city [25
]. Pikine is a product of this displacement and is located about 10 km from central Dakar.
Pikine was founded in 1952 as part of the French clearing out of squatter settlements in central Dakar [27
]. Much of it was settled through informal urbanization processes in the 1970s and 1980s [17
]. This urbanization was unplanned and occurred relatively quickly, and thus networked services such as water and sewerage were not established prior to settlement. These immigrants were generally people leaving the countryside because of environmental and economic factors. New settlement waves were particularly common during drought years, as people in rural areas were faced with dwindling agricultural returns and increasing costs of living, especially in the 1980s [28
]. When migrants came to Pikine, they often settled in areas that were formerly wetlands but had turned into dry patches suitable for settlement [29
]. The 1970s and 1980s were relatively dry climatic periods in Senegal, so the low-lying areas that constitute much of Pikine were dry, and water tables were below average depths [17
]. As ground cover has changed from wetland or vegetation to densely populated, largely unplanned settlements, soil compaction and drainage have become major issues in the region. Land cover in Pikine today is dominated by bare soil and built landscapes, with little vegetation to enable infiltration of water to the soil [18
This lack of natural drainage and infiltration is exacerbated by the lack of infrastructure to facilitate the evacuation of surface water [16
]. So far, although some networked infrastructure is under construction, the largest infrastructure project is the construction of catchment basins across Pikine city. These basins, four of which exist in the Djida Thiaroye Kao Commune, were placed in low-lying areas of the commune as a collection point for various surface waters which naturally flow to the lowest areas [16
]. Before the construction of the basins, these areas were some of the worst flooded neighborhoods, and thus the houses were razed, and basins created in their place. These basins have alleviated some, but certainly not all, of the localized flooding, and they have created a host of other problems that are described in the results and discussion sections.
Compounding issues from the lack of drainage are the impacts from rising water tables. Most of the population in Pikine, and Djida Thiaroye Kao in particular, use latrines or septic tank toilet facilities because of the lack of a networked, piped sewerage system. Some of this sewage is transported out to the ocean via trucks, but much of the waste filters through the soil locally and both contributes to the rising groundwater levels and potentially contaminates this water. As water tables have risen, sewage levels in septic tanks and latrines have also risen. Households then find their latrines or pits full and dig other holes nearby in which they can dispose of this waste. Disposal of household wastewater also poses a problem for most residents. The most common way to dispose of waste is to use public streets or alleyways as wastewater disposal sites, with the water infiltrating the soil or evaporating at the surface. Households that live close to water catchment basins sometimes dispose of household wastewater directly into the basins.
Another contribution to the rising water tables is the increasing rainfall regimes since the time of initial settlement [17
]. As stated earlier, most of Pikine was settled during periods of prolonged drought. The low-lying areas that make up most of the city had much lower water tables at the time of settlement than the long-term average water table depths. Rainfall patterns returned to normal during much of the 1990s, and water tables rose and returned to a more average depth. Flooding did not immediately accompany this return to normal rainfall and water table levels but instead began after rainfall increased significantly in 2005. In fact, from 1970 until 2005, Dakar experienced some of its lowest recorded rainfall levels, but since then, they have remained high with intense periods that cause heavy flooding [2
Rising water tables and the lack of sanitation have contributed to the severe contamination of the Thiaroye Aquifer which underlies most of Pikine [30
]. This aquifer was the source of Dakar’s drinking water until the mid-2000s, but high levels of nitrates, caused primarily by the infiltration of wastewater, made the aquifer’s water too expensive to treat and deliver [19
]. Dakar’s networked water system stopped using the Thiaroye Aquifer, and all the water that was once pumped out now remains in place. The ever-growing population of the region, coupled with climate change-induced patterns of erratic rainfall regimes and the ceasing of use of the underground aquifer, has made flooding a recurrent and often catastrophic problem [16
]. Previous research has demonstrated that severe contamination continues at wells and boreholes across the city of Pikine and the Commune of Djida Thiaroye Kao, and this groundwater often makes its way to the surface during flooding periods [16
]. The impacts of contaminated water are but one of the many economic and health impacts of flooding in the region.
Not only does Pikine suffer from development and environmental problems that contribute to flooding, it also faces economic and social challenges. In 2005, just as increased rainfalls were causing regular flooding, Senegal’s poverty reduction efforts stalled [32
]. The floods themselves are one explanation for this decline in economic growth. A 2011 survey found that 25% of people in Pikine do not have their nutritional needs met, 78% live in households that are deprived of basic needs such as water, electricity, sanitation, or proper construction, and 33% are considered to live in poverty [32
]. Compared to other cities in Senegal, Pikine is ranked last in terms of the number of homes with running water, with toilets connected to the sewer system, and with electricity [33
]. Although the entire Dakar region experiences floods, they are more severe and affect more people in Pikine than in other areas. Thus, many of the residents of Pikine lack the financial resources to both prepare for and recover from floods.
1.2. Overview of Flood Impacts in the Dakar Metropolitan Region
Floods create significant economic impacts by damaging homes and possessions, increasing economic vulnerability, and forcing people to spend time on flood prevention or clean-up rather than on income-generating activities [2
]. People may also forgo medical treatment because of a lack of ability to pay for service [21
]. Poverty has been linked to the difficulty for households to implement long-term strategies for flood mitigation [18
]. Instead, residents implement short-term strategies such as building a small wall in front of their house or using sandbags to create flood barriers [18
]. They end up spending more money over time on these short-term measures because they need immediate relief rather than saving for a more effective and expensive permanent solution. These residents are often unable—or unwilling—to move to areas free from flooding because these new places might be further from work or too small for Dakar’s typically large families [34
]. Thus, the city’s poor are stuck in a flooding cycle. They stay in these flood-prone areas to be close to work, but then the floods disrupt transportation and mobility, and residents lose income [18
]. Compounding these problems is the fact that Dakar lacks adequate flooding and greywater infrastructure. Only 7% of households in Dakar have storm water drainage outside their home, and only 5% of those drains actually work [22
The expected increase in the intensity and frequency of floods will then increase both disease and mortality rates [3
]. The most commonly associated disease with flooding is malaria, and its infection rate increases during flooding periods because mosquitoes breed in standing and stagnant water [21
]. Disease risk can persist even after floods recede, since mosquito eggs can survive on damp soil for several days, and transmission increases as the proximity to breeding grounds decreases [36
]. In Pikine, studies found that malaria affects 93% of households [2
] and, in another suburban city of Dakar, it affected nearly half of all patients seen at a health center [37
]. Floods lead to standing water which can also contribute to skin disease. This is especially true when skin is submerged in contaminated flood water for a prolonged period of time [38
Floods can contaminate drinking water sources and cause diarrhea, which is the leading cause of morbidity and mortality in children under the age of five in the developing world [39
]. In Pikine, diarrhea is more common in households that experience flooding [2
], and in urban Senegal, more broadly, bacterial diarrhea is most prevalent during the rainy season [23
]. In addition to contaminating drinking supplies, flood water can disrupt sewerage systems [41
] and prevent people from seeking medical services by flooding healthcare facilities [21