Another ‘June’, another flood: What the maps have been telling us all along

Every June, the capital city, Accra, collectively braces itself for what has become an unfortunate annual ritual. Yet beyond the headlines and social media videos lies a deeper question: why does flooding continue to affect the same communities year after year and now areas that never got flooded despite decades of appeals and interventions?

I remember working on flood-risk and spatial analysis projects and noticing something striking. When flood reports were plotted on a map and compared against elevation, drainage corridors, settlement growth and runoff paths, patterns immediately emerged. The floodwaters were not behaving randomly. They were following geography. In many cases, the maps could predict where vulnerabilities existed long before the first storm clouds appeared.

That realisation changed how I viewed Accra’s flood problem. It is not simply a rainfall problem. It is geography, urbanization, watershed management and planning problem. The maps have been telling us this story all along.

Understanding the problem

Research consistently identifies the Odaw-Korle Basin as the heart of Accra’s flood challenge. Large volumes of runoff generated across northern and central Accra converge through a limited drainage network before reaching the sea. Flooding therefore occurs not only because of rainfall intensity but because of the speed and volume with which water reaches downstream bottlenecks.

Geography and the role of DEMs

Digital Elevation Models (DEMs) reveal a clear pattern. Higher elevations around Kwabenya, Oyarifa, Adenta and surrounding communities generate runoff that naturally flows toward lower-lying areas such as Alajo, Avenor, Kaneshie and portions of the Odaw corridor.

A community may experience flooding from rainfall that occurred several kilometres away because all runoff eventually converges within the same ‘unready’ drainage system.

Urbanisation and runoff

Urban growth has dramatically altered Accra’s hydrology. Wetlands, open spaces and vegetated surfaces that once absorbed rainfall have increasingly been replaced by roads, housing developments and commercial infrastructure. We live in an Accra where high rainfall on the outskirts of the city fills our drains.  The result is greater surface runoff, faster concentration times and higher peak flows entering drains.

At the same time, structural developments on wetlands and floodplains have reduced the landscape’s natural ability to store excess water.

Government efforts so far

Successive governments have invested heavily in drain construction, desilting programmes, channel improvements and flood mitigation projects such as GARID. These interventions have produced localized improvements and reduced risk in some areas.
However, most interventions have focused on conveying water faster through the drainage system. As urbanization expands and runoff volumes increase, drainage improvements alone struggle to keep pace. The result is that flooding reappears in different forms despite substantial investment.

Lessons from around the world

Tokyo uses giant underground flood diversion tunnels and storage chambers. Rotterdam integrates water plazas and flood storage parks into the urban environment. Copenhagen redesigns public spaces to temporarily store floodwater. Singapore combines stormwater management with water resource planning. Seoul emphasizes watershed management and upstream retention. The common lesson is that successful cities do not rely solely on drains. They store water, slow down water and then move the remaining water efficiently.

A GIS-led solution for Accra

Modern GIS allows planners to identify runoff generation zones, flow accumulation corridors, drainage bottlenecks and vulnerable populations. By integrating DEMs, rainfall data, land use, drainage networks and population data, flood management can become predictive rather than reactive. Beyond mapping existing conditions, GIS can be combined with hydrological and hydraulic flow models to simulate how water moves across the landscape during different rainfall events. These models enable planners to estimate runoff volumes, predict flood depths and extents, assess the performance of drainage infrastructure, and evaluate the effectiveness of proposed interventions before they are implemented. By modelling various scenarios, decision-makers can better understand where risks are highest and where investments will yield the greatest benefits.

Instead of asking where floods occurred yesterday, we can identify where floods are likely to occur tomorrow, how severe they may be, and what measures can be taken in advance to reduce their impact.

My perspective: intercept water upstream

A sustainable solution to Accra’s flooding problem requires a shift from simply reacting to floodwaters to managing them strategically across the entire watershed. Successful flood management is built on three principles: “preventing” the water from reaching Accra, slowing water and moving water efficiently into the sea. Unfortunately, Accra has focused predominantly on the third approach of constructing and expanding drains while paying comparatively little attention to upstream water retention and runoff reduction. Let’s call a spade a spade; urbanization isn’t going to halt. As urbanization continues to increase, the increasing volume and speed of surface runoff will eventually overwhelm drainage infrastructure alone. By capturing and slowing stormwater before it reaches the Odaw-Korle system, pressure on downstream drainage networks can be significantly reduced.
Flood reservoirs should not be viewed as idle infrastructure waiting for the next storm. In rapidly growing cities such as Accra, Aburi, Tema, they can function as multipurpose sustainable assets, reducing flood risk during the rainy season while providing water storage, groundwater recharge, urban agriculture opportunities, and ecological benefits throughout the year. The most sustainable flood-control infrastructure is infrastructure that delivers value every day, not only when it rains. In essence, the most effective flood management strategy is not simply to move water faster through the city, but to ensure that less water arrives there all at once.

Alongside upstream water retention, Accra must invest in smarter drainage engineering. This includes redesigning critical drainage corridors, increasing conveyance capacity, creating alternative discharge routes, and applying hydrological modelling to optimize how water moves through the city. A well-engineered drainage network distributes flows more evenly, minimizes bottlenecks, and reduces the likelihood of localized flooding during intense rainfall events. The city must therefore adopt a more balanced strategy that includes restoring wetlands, developing retention ponds and detention reservoirs, protecting floodplains, more efficient drainage systems and integrating green infrastructure into urban planning.

How government can win Ghanaians

Government can build public confidence through transparent, data-driven flood management. This includes publishing flood-risk maps, protecting wetlands, enforcing planning regulations, investing in retention infrastructure, deploying real-time flood forecasting systems and integrating GIS into urban planning decisions.

Conclusion

Another “June” or rainy season should not automatically mean another flood. Accra has technical expertise and planning tools to significantly reduce flood risk. The challenge is no longer understanding the problem. The challenge is implementing solutions that address root causes rather than symptoms. The maps already show us where water flows, where vulnerabilities exist and where interventions will have the greatest impact. The question is whether we are prepared to act on what those maps have been telling us all along.

The writer is Geographic Information Systems (GIS) Specialist

 BY ELVIS SIEGU

Follow our WhatsApp Channel now! https://whatsapp.com/channel/0029VbAjG7g3gvWajUAEX12Q