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Rainwater flooding in streets and how to avoid it

Rainwater flooding in streets and how to avoid it

Cairo streets are suffering rainwater flooding. Photo courtesy: @monasosh

In the past few days, we have seen how we’re greatly suffering from rainwater flooding. With the significant environmental changes, we are currently facing more rainwater every year. What normally happens is rainwater flows till the nearest drain. If the rain water falls on green planted areas, the land absorbs the water till it is saturated.

However, sometimes the rain gathers and can’t flow to the nearest drain. This is because the rainwater is much more than the system can handle. The street therefore will hold the extra water until it can make it in the system. This can lead to major structural problems for paved surfaces and outdoor buildings if they remain for a long time underwater.

Here is how the street infrastructure is designed to deal with rainwater flooding:

Treating the sewers blockage

The right system for rain water sewer is that rain water falling on the street, runs across the pavement to the gutter, and along the gutter to an outlet. However, the rainwater takes rubbish and grit with it, which blocks the sewer. Therefore, the sewers need frequent clearing and de-trashing from the solid substances that come along with rain.

Sewers blockage causing rainwater flooding
Sewers blockage causing rainwater flooding

Spread Calculations

On higher speed roads and highways, engineers consider the spread calculations. The sewer design includes calculations of how far water spreads from curbs towards the street.

In order to keep the water off the traffic lane, the spread calculation is much smaller. Consequently, the water will gather only couple of feet during a rain event. In residential areas however, water can gather for some time till it runs to the sewer while leaving room for cars to move.

Spread calculations for rainwater on highways
Spread calculations for rainwater on highways

Large Pipes & more inlets

Incorporating larger diameter pipes and more inlets is another effective way to keep water out of the street. More inlets that are closer together make more water roll away faster on the busy highways. This greatly helps to avoid after rain water flooding in the streets. In that case, the budget comes as an important aspect as more pipes can be very expensive.

Rain inlets and pipes. Photo courtesy: conservationcorps.org
Rain inlets and pipes. Photo courtesy: conservationcorps.org

Harvesting rainwater

Considering the current environmental situation, harvesting rainwater can be a sustainable solution. We can make use of rainwater falling on our homes and landscape in several purposes. This is through raising paths and patios and sinking all planting areas to capture the rain flow. Preferably choose native plant that can absorb and hold water in their root systems. Therefore, we can turn street rainwater from a problem to a resource.

Sidewalk bioswale treats street runoff in Portland, OR - Photo courtesy: greywateraction.org
Sidewalk bioswale treats street runoff in Portland, OR - Photo courtesy: greywateraction.org

Another source of harvesting rainwater is the roof. Installing a water catchment system for roof rainwater is simple. It can help store water for outdoor irrigation. As roof water gathers in the gutters and runs to a pipe towards the tank. Water can then be used for irrigation.

Gallons of rainwater storage - Photo courtesy: greywateraction.org
Gallons of rainwater storage - Photo courtesy: greywateraction.org

The climate change is already taking place and its consequences are no longer deniable. We’d better collaborate and make a change towards our urban environment.


An architect who’s passionate about movies, design, and advertising. Living for the art of storytelling in different ways, and always seeking to write inspiring stories about good things in the world.