Urban planners have disclosed that a storm water management plan being devised could be the sustainable solution to manage floods that have ravaged the different suburbs of the City of Kigali.

Storm water is surface water in abnormal quantities resulting from heavy rainfall and experts say the high volume of this water in Kigali is being caused by rapid urbanisation that has no sustainable way for managing floods.

Benon Rukundo, the Acting Director of One Stop Centre in the city told The New Times that they have embarked on a study on how best to manage storm water and that it is being done in collaboration with Water and Sanitation Corporation (WASAC).

"With rapid urbanisation and more plots being developed, more floods could hit the city if there is no storm management plan,” he said.

Although he didn’t exactly mention when the study will be completed, he said it will be carried out and implemented in different phases.

"The study is going to map all watershed catchments areas that are causes of the floods and their confluence so that we can devise appropriate technologies to reduce the pressure of storm water flowing into drainages,” he said.

Rukundo said that after mapping the flood hotspots, the city will come up with technologies that treat storm water by filtering and removing waste at established retaining water points before being discharged into wetlands and rivers.

"The same study will also inform the decision to rehabilitate ravines and drainages. It will also help us to provide construction permits for residents in a certain watershed catchment with specific recommendations to control storm water,” he said.

Poor drainage

The official said that where it is possible, besides rain water harvesting, water permeability in homes can be checked through establishing gardens and adding proper drainage of runoff water from homes without causing floods is the best approach.

"Currently, the prime cause of floods is high pressure of storm water that is beyond capacity of existing drains. What is suitable is approaches to drain storm water and get treated before flowing into wetlands,” he explained.

Currently, the City of Kigali is facing a Rwf30 billion deficit for rehabilitating and expanding over 40 drainages that can control floods.

A $400million investment

Rukundo said the storm water management plan will be in line with the National Adaptation Plan.

According to the 10-year climate action plan to adapt to climate change recently submitted to the United Nations Framework Convention on Climate Change (UNFCCC), Rwanda committed to invest $400 million in increasing the percentage of urban population in areas covered by master plans with storm water and drainage management considerations over the next years.

"As settlement is upgraded, storm water management must also be integrated. We Nyarugenge District,” he said.

Rwanda Water Resources Board is also set to establish telemetry stations to monitor the trends or peak flow of rivers, drainages and other flood hotspots as part of early warning systems aimed at minimizing the likely impacts of floods and plan for flood-resilient infrastructure.

What experts say

Aimé Tsinda, a researcher and senior lecturer in the University of Rwanda, College of Science and Technology told The New Times that finding sustainable solutions to flooding in Kigali requires first understanding clear causes of floods.

"Storm water runoff has become a significant problem in Kigali and one of the causes is extended urbanization,” he said.

The increase in urban areas has considerably altered the natural landscape by replacing previous land cover with impervious materials and raised a number of environmental and economic concerns, he explained.

"But by developing more green spaces, the City of Kigali can reduce runoff problems more effectively. To control the flow of runoff, some existing curb can be removed and curb outlets can be installed at carefully chosen intervals which will allow storm water to flow onto well vegetated areas and therefore avoiding erosion and flooding,” he said.

Tsinda said that an overall planning and design based on upgrading the hydraulic capacity of the drainage system.

"Sustainable solution requires finding a good application mix of both structural and no-structural measures appropriate for the City of Kigali. This requires an extensive research, involving a number of experts from different backgrounds,” he said.