http://www.idr.co.ug/dfwa-u/gallery.htm
Date: Mon, 3 Jan 2000 02:33:06 -0600 (CST)
From: ADULE <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
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Subject: ugnet_: KAMPALA FLOODS - Any solutions??
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Lately, the hot environmental topics in Uganda and particularly Kampala
have centered on flooding and the Nakivubo Channel. Mayor Sebanna Kizito
in his December 9th 1999 address to members of NGOs blamed the government
for the flooding problem citing its policy of gazzeting lowland areas to
industrial developments. In reply, Y. Nkulabo in his 16th December
posting on Ugandanet wondered how such a governmental policy would cause
the famous Kampala flooding during the rainy seasons. Mwami Nkulabo
advocates for a program that will see the swamps in and around Kampala
drained with added drainage systems.
Kampala's valleys were homes to swamps and rivers like Nakivubo, Kitante,
Lubigi, and Nalukulongo but to name a few. This changed soon after
Dr.Cook discovered in 1903 that mosquitoes spread Malaria. He advocated
for the drainage of swamps and rivers all over British's colonial
territories. Hence, Kampala's once open slow flowing rivers (streams)
like Kitante, Lugogo, Mulago, Nakivubo, and Nsambya vanished giving way to
covered large pipes and open-air drainage channels. Nakivubo was the
largest project with all the other channels draining into it enroute to
Lake Victoria. This policy at that time seemed to solve Kampala's
mosquito and drainage problems.
On the other hand, Kampala City's urbanization program continued to expand
as more concrete, stone, brick and asphalt of pavement and buildings
capped its surface with a waterproof seal. This urban growth increment
meant stormwater runoffs increased in magnitude and destructiveness
(urbanization can increase the mean annual stormwater runoff by as much as
six times). Unable to penetrate the ground, the rain that falls on
unstable construction sites, roofs, streets and parking lots runs off the
surface in greater quantities, more rapidly than the same amount of rain
falling on the spongy surface of a natural field. The rapid stormwater
runoff flows into narrower, shallower floodplains, constricted by
buildings and clogged with sediment causing considerable amount of
flooding especially around Lugogo, Nsambya, and Mulago. It should be
noted that storm sewers transport water from one point to another; they do
not reduce or eliminate water, they merely change its location.
Traditional storm drainage practice protects local streets, buildings and
parking lots from flooding, while contributing to major flood damage
downstream. [Please note that for an urban storm drainage system to drain
water efficiently from roofs, streets, and sidewalks, the flood control
system must be continually augmented to prevent flooding in low lands of
Lugogo, Nsambya, and Mulago.]
Other effects of storm drainage systems apart from flood hazards are
increased water pollution and use. Typically, the storm drainage system
aggravates pollution by delivering slugs of sewage and runoff after storms
into Lake Victoria. Kampala draws it's water from Lake Victoria and must
contend with increased contamination. Since the ground, sealed by pavement
and drained by pipes, absorbs little water, the amount of water stored in
the ground, from which plants obtain their supply, is reduced. This
lowered groundwater is insufficient to sustain plants during dry spells.
No wonder, urban plants haven't been successful in Kampala streets.
Kampala can adopt a number of innovative approaches to its
flood/stormwater runoff problem by:
- Redesigning the straight concrete-lined Nakivubo open-water channel into
a waterway with irregularly shaped edges and a gently sloped vegetated
bank. This is an opportunity to transform a rubble-strewn, filthy, open
channel lined by garbage and derelict land, into a landscaped park lined
with pedestrian and bikeways.
- Setting up bioswales. (Bioswales are created to capture runoff and hold
it until it permeates into the soil or evaporates into the air. The
bioswale is also seen as a creative means of controlling runoff, as it has
the potential to mitigate wetland loss, preserve open space, and improve
the aesthetics of Kampala. As such, the bioswale has hydrologic, chemical
and biological functions).
- Designing the rooftops, parking lots, open spaces to store stormwater so
that it's gradually released into the ground.
- Preserving open spaces in the headwater areas for natural storage
capacity, thereby reducing flooding and the cost of storm drainage
systems.
- Identifying and designating undeveloped urban wetlands as parkland to
soak up and hold water in soil and plants
- Exploiting the aesthetic properties of water without wasting it
Floodwater storage and recreation are compatible in large open spaces
(urban parks) unfortunately, Kampala has none though there are a number of
potential sites. Its' about time Kampala created urban open spaces that
serve multiple purposes of flood control, water quality improvement and
recreational. These are not new ideas at all but rather the rediscovery
of old solutions. Many Urban Parks in North America were originally
designed as flood control and water quality projects. A clear example is
Boston's Emerald Necklace designed as a flood control and water quality
project and not primarily for recreation.
As Kampala City Council (KCC) endeavors to grant a contract to a firm for
the Nakivubo channel, it would be better to secure lowland areas for use
as floodwater storage point. This will go along way in cutting back on
the 95% city water runoff that drains into it. The National Environment
Management Authority (NEMA) has already identified key lowland areas that
KCC should acquire or at least have them gazette as floodplain areas.
This is an opportunity for a strong partnership between KCC and NEMA if
there is none for the benefit of creating an environmentally safe city.
Let's stop inflicting wounds on Kampala's surface because it will save the
city or else we might be creating a "Venezuela-like" catastrophe. Kampala
should strive for more floodwater catchment areas instead of increased
piped drainage systems. By the way, we have hills, why can't we take
advantage of them and let nature do its job?
Adule
__________
bwanika
url: www.idr.co.ug
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