Interdependencies between the Management of Solid waste and Flood risks in Dar es Salaam
By Nathalie Jean-Baptiste, Joseph John Osena and Veronica Olivotto
Dar es Salaam’s December 2011 flood became a reference of disaster and remains today as a warning for local authorities. It has been the city’s most serious flood experience to date causing 20 deaths, injuring more than 200 persons and displacing about 10,000 people (Kiunsi, 2013).
Dar es Salaam is Tanzania’s largest coastal city. It is also an important commercial hub connecting six neighboring landlocked countries through its seaport. Yet, Dar es salaam is exposed to climate related events and vulnerable in particular to flash floods causing significant disruptions to its principal social and technical infrastructure. There are several reasons for this:
First, the city’s population has grown at an exponential rate. The current population and housing census reports an escalating increase of urban population since 1967. Tanzania’s National Bureau of statistics highlights demographic growth in the order of 2,4 million in 2002 and 4,3 million in 2012 (2014). Other global reports signal 5.1 million in 2015 and a projection of 6,2 million people in 2020 (State of African Cities, 2010; UN-Habitat, 2011). This has serious consequences for current and future urban services.
A second reason is the reduced permeability of ground surfaces, partly due urbanization, the extension of sealed surfaces and the rise of built-up structures located in flood prone areas. Many settlements are constructed in catchment zones and several constructions are known to obstruct the natural water flow downstream to the Indian Ocean. This consequently increases flood risks across the city.
Thirdly, insufficient and failing storm and wastewater drainage systems exacerbate the problem; Dar es Salaam’s drainage system is 20 year old (Mwalyosi, 2014). The city lacks adequate drainage particularly in new established neighborhoods and peri-urban areas. Most secondary roads have limited and poorly maintained side drainage. As a result, water not only overflows, but also remains on roads and footpaths during heavy precipitations.
Lastly, inefficient solid waste management prompts the blockage of drainage channels, which ultimately increases the volume of storm water runoff (Sartohadi et al., 2014). In addition, rivers and streams are often used as dumping sites. They receive several tons of polluted loads from industries and solid waste (Mwalyosi, 2014). This accumulates multiple risks including floods (See UrbanARK project www.urbanark.org)
Solid waste is a serious problem in Dar es Salaam. Investigations done by the World Bank in 2011 revealed that the city produced approximately 4,200 tons of solid waste per day. This is around 0.93 kg/cap/day. The triplication of the Dar es Salaam population in the next 15 years naturally implies the triplication of the amount of waste to approximately 12,600 tons per day. In 2012, Dar es Salaam’s largest municipality Kinondoni collected approximately 954 tons/day (Dar es Salaam Municipal profile, 2012). Yet, this remains insufficient and uncollected waste is disposed off anarchically. Solid waste is dumped in open spaces, thrown in storm water drains, valleys and along roads, piled in collection points or covered by plastic bags and also frequently burned.
Poorly managed solid waste and inadequate urban services provision increase flood risks. As the city continues to experience variability in weather patterns, heavy rains during rainy seasons are to be expected and with them come water runoffs across the city.
Several attempts are made to reduce disaster and risks related to flooding. There is for instance, the provision of drainage channels through community infrastructure upgrading projects (CIUP) targeting infrastructure improvement in densely populated areas (Sakijege, Sartohadi, et al., 2014). There are funded development initiatives such as the restoration of the Mlalakua River under the International Water Stewardship Program. The construction of a municipal compost plant in Mabwepande is underway under the program Compost Works funded by the German Federal Ministry for Economic Cooperation and Development and the City of Hamburg (Daily News, 2016). While these efforts and many others emerge, the question of how flood risks are reproduced through solid and wastewater remains pertinent. The fact remains that waste issues need to be at the forefront of environmental discussions and public health agendas as well as disaster reduction and climate. In that regard, Dar es Salaam requires a holistic understanding of solid waste management and how it can help steer climate-proof developments.