Urbanization and floods led to climate change in Dar es Salaam, Tanzania
Geography of Dar es Salaam:
Dar es Salaam is located in the eastern part of the Tanzanian mainland at 6˚51’S
latitude and 39˚18’E longitude. With an area of 1,350 km2, it occupies 0.19
percent of the Tanzanian mainland, stretching about 100 km between the Mpiji
River to the North and beyond the Mzinga River in the South. The Indian Ocean
borders it to the East.
Sand dunes and tidal marshes make up the beach and coastline. Coastal
lowlands made up of limestone stretch 10 kilo meters west of the city, 2-8 kilo
meters north, and 5-8 kilo meters south. Inland, alluvial plains are made up of
a succession of U-shaped valleys with steep sides. The Pugu Hills, which are
dissected and range in altitude from 100 to 200 meters, make up the upland
plateau. The soils of Dar es Salaam are not especially productive, being
dominated by limestones, sandy clays, coarse sands, and mixed alluvial deposits
(Dongus, 2000).
The upland zone, which includes mountainous areas to the west and north of
the city, the central plateau, and the lowlands, which comprise the Msimbazi
Valley, Jangwani, Mtoni, Africana, and Ununio areas, are split into three
ecological zones. The primary zones are depicted in the diagram. Coastal palm
groves, coastal shrubs, Miombo forest, coastal wetlands, and swampy mangrove
trees and reeds make up the majority of the natural vegetation. The diversity
of forest and scrub has been decreased as a result of long-term human
intervention.
Climatology of Dar-es-Salaam:
The upland zone, which includes mountainous areas to the west and north of
the city, the central plateau, and the lowlands, which comprise the Msimbazi
Valley, Jangwani, Mtoni, Africana, and Ununio areas, are split into three
ecological zones. The primary zones are depicted in the diagram. Coastal palm
groves, coastal shrubs, Miombo forest, coastal wetlands, and swampy mangrove
trees and reeds make up the majority of the natural vegetation. The diversity
of forest and scrub has been decreased as a result of long-term human
intervention.
Although most of the country has dry weather from June to September,
coastal locations receive a modest amount of rain during this time. The
southeast monsoon winds (May–September), the northeast monsoon winds
(October–March), the El-Nino Southern Oscillation (ENSO), tropical cyclones,
easterly waves, and the Congo air mass all impact rainfall in Tanzania. The
geographical and temporal distribution of rainfall over coastal locations such
as Dar es Salaam, Zanzibar, Pemba, and Tanga is heavily influenced by land and
sea winds along the Indian Ocean coast.
The mean annual maximum temperature in Dar es Salaam and Zanzibar is
30.8°C, with a mean annual low temperature of 21.3°C. The average diurnal
temperature difference is 9.2 ℃, which is lower than in inland locations.
70 % of Dar es Salaam's population lives in informal settlements, with more
than half of them subsisting on a weekly salary of $1. These communities lack
appropriate infrastructure and services, and therefore are particularly
vulnerable to the negative effects of floods. When poor solid waste management
and sanitation methods are paired with rain, the water becomes contaminated,
and illness spreads. In the absence of solid, forward-thinking planning
initiatives, climate change will worsen these problems.
Vulnerability to current climate:
Through review of existing literature, surveys involving over 500
households, community focus group discussions and in-person visits with
government, non-government, and community development organization officials,
detailed information on existing vulnerability to climate variability among
poor residents of informal settlements were obtained. The surveys were
conducted in high-risk flood regions, with a few non-risk areas thrown in for
comparison.
The informal settlements are particularly vulnerable to climate change.
Flooding is common, and it is caused by a combination of climatic and
non-climatic reasons such as overcrowding, dumping of sewage and solid waste
into rivers and channels, and rubbish or illegal building blocking storm
drains. Apart from property loss, problems such as a lack of potable water, poor
sanitation, extensive usage of pit latrines that overflow often, and unsanitary
behaviors make many people of these communities vulnerable to disease,
especially after floods.
Malaria, lymphatic filariasis, cholera, dengue fever, and diarrhoea, among other illnesses, are common among the residents of these communities. Drought also affects Dar es Salaam, which tends to increase illness incidence when clean water becomes limited. Drought has negative consequences for the city's electric power output, as hydropower is a major source of energy. Floods, droughts, and other climate variables (humidity, high temperatures) have an influence on the poor, many of whom work in the informal sector and sell their wares on the street.
Climatic trend analysis:
In Dar es Salaam, climate patterns over the last four decades show growing
maximum and minimum temperature trends. Precipitation patterns are less
apparent, although they appear to show a decrease in the number of rainy days
each year, as well as a high degree of unpredictability. The amount of rain
that falls is likely to rise. Increased coastal flooding would come from rising
sea levels. Flooding would be exacerbated by environmental deterioration and
greater storm surges. Several of Dar es Salaam's El Nino occurrences appear to
have played a role in Salaam's significant floods during the last three
decades.
A flood modelling
experiment was carried out using a digital elevation model and a hydrodynamic
model to assess how climate change may affect flood spatial extent in Dar es
Salaam's unplanned settlements during the future decades. Inundation caused by
floods with varying return times. Reduced annual mean rainfall in the future
years might lead to additional droughts in areas of Tanzania, threatening food
and water security and having far-reaching indirect consequences, such as
reduced energy availability for the city's poor and an increase in disease prevalence.
However, there are no specific drought forecasts for Dar es Salaam.
Climate change might
increase the vulnerability of Dar es Salaam's urban poor in a variety of ways.
Climate change is projected to increase the intensity of rainfall in Dar es Salaam,
worsening floods. Coastal erosion and deterioration would be worsened by an
increase in sea level. Coastal storms may become more powerful and accompanied
by higher storm surges than they are now, putting coastal towns at danger.
Increased temperature may boost humidity levels during wet seasons, posing a
risk of insect and disease outbreaks. A prolonged drought would have a
detrimental effect on water and electricity, as well as health and agriculture
in a city.
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