Greater Banjul Flooding Driven by Local Infrastructure Challenges, Not Casamance, Scientist Says

Written by: Alieu Jallow

An environmental scientist has challenged claims by Minister of Works, Transport and Infrastructure Ebrima Sillah that recurrent flooding in the Greater Banjul Area is primarily caused by floodwaters flowing from Senegal’s Casamance region rather than by local infrastructure and environmental challenges.

The comments come after Ebrima Sillah attributed severe flooding in parts of the Greater Banjul Area to floodwaters originating from Casamance, remarks that have circulated widely on social media.

Seeking expert analysis, The Fatu Network spoke with Dr. Nfamara K. Dampha, Lead Scientist at the University of Minnesota and Africa NCA, who said the available scientific evidence indicates that persistent flooding in The Gambia is driven predominantly by local environmental conditions, rapid urbanisation, and inadequate drainage infrastructure rather than transboundary flooding.

According to Dr. Dampha, flooding in The Gambia results from a combination of intense rainfall, low-lying terrain, inadequate drainage systems, rapid urban expansion, and environmental degradation.

“In many urban and peri-urban areas, particularly around the Greater Banjul Area, flooding is often driven less by river overflow and more by stormwater accumulation where drains are undersized, blocked by waste or sediment, or absent altogether,” he explained.

He said the continued expansion of settlements into wetlands, floodplains and natural drainage corridors has significantly reduced the landscape’s ability to absorb and channel rainfall. The destruction of wetlands, loss of vegetation and increasing soil compaction have further accelerated surface runoff, worsening flood impacts.

Can Flooding in Casamance Affect The Gambia?

Addressing whether heavy rainfall in Casamance can contribute to flooding in The Gambia, Dr. Dampha said such a scenario is possible under certain circumstances.

“Hydrologically, heavy rainfall in southern Senegal, including parts of Casamance, could contribute to localized flooding in some nearby Gambian border communities where seasonal streams, wetlands, and low-lying floodplains are interconnected,” he said.

However, he stressed that such transboundary flooding is relatively uncommon and is unlikely to explain the repeated flooding experienced in major Gambian urban centres.

He noted that much of the border region remains sparsely populated and retains significant natural flood-absorbing capacity through wetlands, vegetation, permeable soils and floodplains, all of which help slow runoff and reduce peak flood flows.

“In contrast, the most severe flooding in The Gambia is more commonly associated with intense localized rainfall, inadequate urban drainage, settlement expansion into flood-prone areas, and degradation or blockage of natural drainage pathways, particularly in the Greater Banjul Area and other rapidly urbanising settlements,” he said.

Dr. Dampha concluded that while upstream rainfall from Casamance may contribute to localized flooding during extreme weather events, it is generally an unlikely primary cause of the flooding repeatedly experienced across The Gambia.

Evidence, Not Assumptions

The climate scientist, who also serves as one of The Gambia’s lead climate change negotiators at the United Nations Conference of the Parties (COP), said determining whether flooding is caused by transboundary factors or domestic conditions requires scientific evidence rather than assumptions.

He explained that researchers examine rainfall intensity and timing, watershed boundaries, topography, elevation models, runoff pathways, satellite imagery and community-level flood patterns before reaching conclusions.

“If flooding in Gambian border communities occurs shortly after intense rainfall in upstream parts of Casamance, follows known hydrological pathways, and corresponds with rising water levels in connected wetlands, streams, or floodplains, then some upstream contribution may be plausible,” he said.

“However, given the relatively high natural absorptive capacity in many border areas, such cases are likely to be localized rather than widespread.”

He added that where flooding occurs primarily after intense local rainfall, particularly in areas with blocked drains, inadequate drainage infrastructure, filled wetlands, poorly designed road drainage, or expanding settlements in low-lying zones, domestic land-use and infrastructure issues are far more likely to be the dominant causes.

“In practice, while some flood events may involve both regional runoff and local runoff accumulation, the recurrent flooding observed in most Gambian urban centres is more strongly linked to local rainfall, urban drainage limitations, and environmental degradation,” he said.

Assessing The Gambia’s flood preparedness, Dr. Dampha acknowledged that the country has made progress in disaster risk management but continues to face significant challenges.

He identified poor drainage maintenance, weak enforcement of land-use regulations, limited community-level early warning systems and insufficient investment in flood-resilient infrastructure as major constraints.

Among the country’s most urgent priorities, he said, are mapping flood-prone areas, clearing drainage systems before and during the rainy season, preventing construction in wetlands and natural drainage corridors, strengthening local early warning systems, improving municipal drainage planning, restoring wetlands and mangroves, and providing vulnerable communities with effective evacuation and recovery support.

Dr. Dampha also warned that climate change is increasing both the frequency and intensity of heavy rainfall across West Africa while contributing to sea-level rise, coastal erosion, salinity intrusion and compound flooding.

“In The Gambia, this means rainfall-driven floods can become more intense, while coastal and riverine communities face greater exposure due to rising sea levels and ecosystem degradation,” he explained.

He said long-term adaptation should prioritise climate-informed land-use planning, upgraded drainage infrastructure, coastal protection measures, wetland and mangrove restoration, floodplain protection, green zoning regulations and nature-based infrastructure solutions.

“The country also needs stronger climate data systems, improved hydrological monitoring, and effective enforcement of environmental regulations so that adaptation decisions are guided by evidence rather than crisis response,” he concluded.