Conservation of river regimes — A solution to flooding across the country

Engineer Julius Mugun, CEO, NWHSA

Climate change is increasingly pushing weather to extreme ends, and these extremes are now happening back-to-back.

Kenyans must therefore be aware that whenever an advisory comes from the meteorological department, they need to be wary, especially in areas prone to floods.

Communities should remain alert, monitor the environment, and people living in fragile highlands—where landslides sometimes occur—should find safer places whenever warnings are issued.

Preparedness and awareness are critical as the country faces more unpredictable weather patterns.

This is also a high time, particularly in rural areas when the government is talking about food security, to consider land consolidation.

Building homes within a particular area allows more land to remain available for cultivation. Such an approach would reduce subsistence farming and increase areas under commercial farming.

If we increase land under cultivation in a more organised way, we shall harvest water for irrigation and expand productive agricultural land.

In many ways, we simply need to return to the nuclear farming approach practised by our grandfathers, where farming and settlement were planned in a way that maximised land use.

Environmental conservation must also be part of the solution.

We need to plant more trees to conserve the environment and protect water sources. Equally important is the conservation of riparian land.

Riparian land should be allowed to work for us. Chiefs and members of the National Government Administration should help ensure communities plant trees such as bamboo that conserve water, as well as fruit trees that benefit local households.

When riparian land is preserved, we increase the length and sustainability of fresh water resources.

Farmers should not be allowed to cultivate right up to the riverbanks. When this happens, the river regime is affected. A river can migrate underground for long distances and leave behind dry land where water once flowed.

Allowing water to flow freely from upstream to downstream ensures it can be discharged safely into lakes or oceans.

Protecting river regimes, therefore, becomes essential in reducing flooding and maintaining water systems.

As an Authority, we are also planning trenching to encourage changes in farming patterns. When land is cultivated without proper soil conservation, siltation occurs.

By trenching the land, water can flow more freely and eventually reach lakes without carrying large amounts of soil.

Water is essential for dignity and life. However, when it cannot be controlled, it becomes a nuisance.

At the National Water Harvesting and Storage Authority, we are working to ensure water is managed and tamed so that it behaves the way it is supposed to.

Urban flooding, especially in Nairobi, presents a different but related challenge.

Nairobi is full of pavements and roofs, yet it has very little grass canopy or tree cover to absorb rainfall.

Even when rainfall levels are not extremely high, the volume of water pouring from roofs becomes overwhelming because it has nowhere to sink or perforate into the ground.

Instead, the water accumulates and flows quickly into downstream channels. When you look at the whole of Nairobi, you see water simply flowing everywhere, with almost no drop allowed to infiltrate the ground.

Naturally, the water cycle requires evaporation from leaves, oceans, lakes, and rivers, after which moisture moves to the highlands where mist condenses and forms rainfall.

When it rains, water should infiltrate the soil, flow gradually, and eventually return to the oceans.

In Nairobi, however, we lack spongy areas where water can be held temporarily. This means we need detention basins that can hold water in specific places before it flows downstream.

Without such systems, runoff combines into powerful flows that overwhelm drainage channels.

The City has both natural and artificial waterways that are meant to carry water from their catchments.

However, massive construction in Nairobi has overwhelmed these waterways, leading to spillovers into built-up areas.

Road design has also contributed to the flooding problem. Many roads were originally meant to follow the natural terrain—from upper slopes to valleys and then up again. In practice, some roads now cut across natural waterways.

During heavy rains, traffic sometimes stops in these low areas, which are essentially water paths. People caught in the middle become vulnerable because they are directly in the waterway, which explains why some motorists were swept away during recent floods.

Cities normally have floodplains—areas where water is allowed to spread temporarily when waterways fill up.

These are often the same riparian lands that have been encroached upon. When traffic or buildings occupy these floodplains, they become the most affected during floods.

One possible solution is to elevate certain road sections using pillars so that water can flow underneath without disrupting traffic.

Another is to create more artificial channels to move water away from the city and store it safely.

For example, floodwater could be diverted through tunnels into storage areas such as parts of the Nairobi National Park, where it could later support wildlife.

In Nairobi, the county government is responsible for urban management. The floods experienced in the city are largely not from upstream catchment water, but from poor urban drainage systems that should connect to natural waterways.

Many cities in Kenya are not properly planned. Houses are built, roofs installed, gutters fixed, and water is simply drained onto roads.

Instead, this water should be directed into channels designed to carry large flows.

The problem, therefore, lies largely in the planning and enforcement of existing policies.

National Water Harvesting and Storage Authority is working on regulations that will support a water harvesting program in the city of Nairobi in partnership with the county government and other stakeholders.

The goal is to harvest urban runoff and store it rather than allowing it to cause destruction downstream.

Areas hardest hit by floods in Nairobi were those near rivers and natural waterways that carry stormwater.

Unfortunately, stormwater channels are often overwhelmed. Even major infrastructure, such as the expressway, collects large volumes of water and channels it to the ground with significant force.

We have engaged the city leadership on these challenges. Progress may be slow, but some inroads are being made. Our focus is to ensure such flooding incidents do not recur.

Across the country, the National Water Harvesting and Storage Authority has been implementing flood mitigation programs.

Much of our work has focused on major rivers and plateaus to prevent water from entering commercial centres.

In Budalangi, we managed River Nzoia in such a way that the area has been largely protected. Recent flooding there was mainly due to backflow from Lake Victoria.

We constructed dykes in areas such as Musoma, Sigomere, and parts of the Mau Mau region to prevent lake water from flowing into settlements.

As a result, primary schools, churches, and commercial centres that were once frequently flooded have reopened.

We also constructed dykes in Kano East at a place called Ogenya, where schools and farms were submerged in water.

Ogenya Primary School and nearby farms are now protected, evacuation centres have closed, and residents have returned to their homes.

In Meriti in Isiolo, which used to be affected by floods from nearby hills, we created channels to guide water safely away from settlements.

Similar work was done in Waride in Lamu, where we controlled water flowing from upstream into the ocean.

These projects manage surface runoff and reduce flood risks for communities.

Flooding in Nairobi has now reminded us that we must also focus more attention on urban centers, especially cities such as Nairobi, Mombasa, Kisumu, Nakuru, and Eldoret.

The country needs a robust program to capture floodwaters and prevent unnecessary loss of life and economic disruption.

Recent floods left many people stranded—some slept in offices while others remained on roads because transport routes became impassable.

The government is now working to address the situation and ensure that future floods are better managed across both rural and urban areas.

Article by Engineer Julius Mugun, CEO, NWHSA