What should be done to address the recurrent problem of flooding in Dar

The recent widely-reported flooding in the City of Dar es Salaam was hardly news to long-standing city residents. It is an expected annual event, whenever there is a downpour. In 1986, Prof Kulaba, of the then Ardhi Institute, wrote, in a chapter published in a book titled “African Cities in Crises” that in May 1986, flooding in the Mtoni area of Dar es Salaam as a result of heavy rains, destroyed more than 200 houses. That was 37 years ago. The flooding spree in Dar es Salaam and other urban areas continues to this day, without let or hindrance.

Most of the time, blame has been put on those low income households building in river valleys.

However, this noise is currently being drowned by the irrefutable evidence that flooding is a result poor management of surface water runoffs which is an outcome of many factors.

The city lacks an integrated system of drains that can safely transport surface water. Many roads are constructed without any drains. In the few cases where drains are constructed, they are poorly designed and poorly maintained, and can be seen blocked, filled with sand, solid waste or other debris, or, are outgrown with natural vegetation.

Many times, such drains end up abruptly, leading to “nowhere” and are unable to discharge the water safely.

Since time immemorial, concern about flooding in the city of Dar es Salaam has been equated to what happens in the Msimbazi River Valley, at Jangwani. True, Msimbazi river, at 35km, is the longest in the city, and combined with its major tributaries such as rivers Ubungo, Kinyerezi, Zimbili, Sinza (Ng’ombe), and Luhanga, it can claim holding the hall of fame as a natural city phenomenon, but the question of urban flooding must be seen as being city wide.

However, true to tradition, the recent city flooding saw two ministers and a regional commissioner, converging and rubbing shoulders at Jangwani. The President herself gave directives, on what to do at that spot.

To address flooding, the city must be seen as a whole. On the one hand, you need a city-wide drainage system which provides channels for carrying excess rainwater which would otherwise flood low-lying areas and causes significant problems, including property damage and even loss of life.

It also provides channels for storm runoff, treated wastewater, and canalization of rivers and streams.

It should be remembered that built-up areas need to be drained to remove surface water runoff from impervious surfaces such as paved streets, car parks, parking lots, footpaths, sidewalks, and roofs. Concretization and cementing typical of urban areas increases water run-offs.

City drainage and flood control would include the integration of natural drains, such as urban rivers and streams, as well as other water bodies, such as urban wetlands, ponds and lakes. Unfortunately, many of these have been built upon, or their areas of functioning have been greatly reduced by the encroaching human activities. This tends to increase the velocity of water in these rivers, leading to erosion, flooding and damage to property.

Dar es Salaam has over 20 significant rivers, and countless rivulets and streams. Urban expansion has blocked many of these natural waterways, which are now largely seasonal, due to human interference. They however, spring to life when it rains, imposing vengeance with fury, that results into floods.

Major rivers of Dar es Salaam include Mpiji, Nyakasangwe, Burumawe, Dovya, Tegeta, Ndumbwi/Manyema, Mbezi, Mlalakuwa, Sinza, Ubungo, Luhanga, Kinyerezi, Kijitonyama, Msimbazi, Mzinga, Kizinga, Mbagala, Yombo, Kinyamwezi, Mwera, Nguva/Ukooni, Bandari, Mbugani, Kiserawe, Mtandika, and Mbezi II. These must be part and parcel of plans to control flooding and improve the urban environment.

Concern with urban drainage and flooding in Dar has been partial, included in projects supported by development partners, such as the Sustainable Dar es Salaam Project (1992-2003), Community Infrastructure Upgrading Project (CIUP), and the current DMDP. Time has come to use local capacity to prepare citywide drainage and flood control plans. These would include artificial drains, especially along all roads; and links to water bodies such as rivers and the Ocean.

The rivers would need to be rehabilitated, preserving their floodplain areas by declaring and demarcating river valleys to be hazard areas as provided for in the Land Act; by undertaking: river and wetland restoration programmes, periodic maintenance of drains and water channels; and public education and regulation, about abstaining from construction on wetlands and haphazard disposal of waste. It needs to be emphasized that urban wetlands are important in controlling flooding and supporting biodiversity and should be included into a larger picture of managing the urban environment.