Volume 11, Issue 3,
July-September 2022
CONTENT
Chair's Foreword
Increasing Frequency of
Extreme Flood Events in African Urban and Rural Areas
Earth Science Events
References and selected reading
Chair's Foreword*
In
this issue we report on marked increase in the frequency of extreme flooding
events on the continent, and in West Africa particularly. The report is timely
as 2022 has been one of the worst years on record for the continent in terms
of urban flooding due to extreme rainfall.
Increasing Frequency of Extreme
Flooding Events in African Urban and Rural Areas
In
recent years we have seen the increasingly more frequent flooding of urban
areas in Africa, and West Africa in particular.
Toure [1] notes recent West African flood events in Abidjan (May 2017,
June 2018), Ouagadougou (2009, 2015) and Dakar (2009, 2017) as well as other
major capitals (Lagos, Accra,etc). We can presently add to this series of
extreme events in noting that the recent 2022 floods occurring throughout West
Africa have displaced over a million people in Nigeria alone and resulted in
the loss of hundreds of lives [2]. Ayesha Tandon in Carbon Brief, November
2022 succinctly reports on the research of Otto et al [3] which claims
that the deadly level of rainfall in the region in 2022 was made 80 times more
likely due to climate change.
In Nigeria the flood waters displaced over a million people and over a
million hectares of farmland were damaged. Food security in the region was also
negatively impacted due to the rise in prices as crops failed and yields fell.
In Nigeria and Niger the floods were amongst the deadliest on record.
Chad declared a state of emergency faced with the heaviest rainfall in 30
years. The release of Cameroon's Lagdo Dam exacerbated matters and the
emerging trend in the impact of dams in relation to the increased risk of flood
due to climate change needs to be accorded critical and serious monitoring,
especially where dam is part of an infrastructure scheme that is not complete;
as in the case of the Lagdo Dam, which was supposed to be accompanied by the
construction of another dam in Nigeria, which is still not built.
Otto and colleagues' climate science work partly addresses a new area of
climate science known as "attribution", which attempts to establish
the "fingerprint" of climate change on extreme weather events. This
would appear to place climate science on a more rigorous footing where the
input of climate change can be established and quantified.
To conduct attribution studies scientists use models to compare the world
as it is today with an ideal world that is untouched by human activity, and
without human induced climate change. The study of Otto et al attempts to
establish the "signature" of climate change in West African rainfall.
The main causes of flooding in West African urban regions were identified
by the study of Toure cited earlier from the CR4D programme:
-
Abundant rainfall (the 2022 studies of Otto et al indicate that floods were
caused by short intense storms)
-
Permeability of the soil
-
Saturation of the soil due to destruction of vegetation in urban and rural
areas
-
unsuitable/poorly maintained drainage/street gutters
-
uncontrolled urbanisation and poor development planning of urban extension
As
the studies indicate - we do in future years expect to see the continued
increase in the frequency of extreme and very extreme weather events. The CR4D
study by Toure suggests urban African regions can be made more
sustainable by the promotion of more green spaces such as public parks and
gardens especially in storm basins and flood prone areas. Also the option is
there to promote the vertical extension of West African cities.
Another more recent study by Turay [4] suggests that little attention is
paid to ecosystem based measures to tackle flood hazards, and they are not used
in managing flood events. The study usefully suggests the need for
intra-african learning from observing how different countries in Africa tackle
extreme flooding and noting which strategies are more successful, and those not
so successful.
Earth
Science Events
December 13, 2022
International Conference
on Agriculture, Biotechnology, Biological
and Biosystems Engineering
VISION:
VENUE: Cairo, Egypt
References
[1]
Toure, N. E., Flood risk reduction under Paris agreement (FLORR-PA) for
three West African capital cities, Climate Research for Development
(CR4D), end of grant workshop presentation, 21-23 June 2021, Nairobi, Kenya.
[2]
Tandon, A., West Africa's deadly rainfall in 2022 made "80 times
more likely " by climate change, Carbon Brief, November 2022.
[3]
Otto, F., et al, Climate exacerbated heavy rainfall leading to
large-scale flooding in highly vulnerable communities in West Africa, ResearchGate, 2022.
[4]
Turay, Bashir, Flood hazard management in a multiple hazard context: a
systematic review of flood hazard management during the COVID-19 pandemic in
Africa, Discover Water 2, Article number:6 (2022)'
https://doi.org/10.1007/543832-022-00014-w
*Board
of the Society of African Earth Scientists: Dr Enas Ahmed (Egypt), Osmin Callis
(Secretary - Guyana/Nigeria), Mathada Humphrey (South Africa), Ndivhuwo Cecilia
Mukosi (South Africa), Damola Nadi (Nigeria), Dr Chukwunyere Kamalu (Chair -
Nigeria).
