According to City Hall, the physical planning of the city in terms of urban planning dates back to post-independence days when the designs were made.
The old drainage was designed to serve less than 500,000 people but the city population has since ballooned to about five million.
Upgrading the system might require demolishing some buildings, which City Hall says is impossible. The construction, especially in the slums, has compounded the drainage problem. Trade activities on road reserves like building kiosks over drainage systems, selling building materials like sand, stones, ballast, and timber some of which end up in the drains have also been faulted for blocking the drains. City residents have also been blamed for dumping solid waste in drainage systems, blocking the flow of water.
An attempt to address drainage was made on April 11, 2018, when Nairobi acquired flusher machines used to unblock drainage systems. It was part of programs funded by the World Ban under the Nairobi Metropolitan Service Improvement Project. The project started in December 2012 and was expected to be completed by the end of May 2019. The whole project costs around Sh500 million and Nairobi alone is allocated 75 percent of the total amount.