Drivers and Spatial extent of Urban Development in Flood-prone Areas in Metropolitan Lagos

Abstract

Urban development in flood-prone areas has created many environmental challenges in many cities in Nigeria. This survey-based study examined the drivers and spatial extent of development in floodplains in metropolitan Lagos. A total of 1,031 (7.2%) buildings out of 14,273 were systematically selected along 211 streets out of 1,403 prone to flood, and a structured questionnaire was administered to heads of households to determine the factors influencing development in floodplains. A Thematic Mapper of 1990, Enhanced Thematic Mapper of 2000 and the Google Earth Landsat of 2014 were also analysed in ILWIS 3.3 Academic and Arc-GIs 10.2 to determine the extent of development in floodplains. The study revealed, in order of significance, closeness to place of work, nearness to market, closeness to children’s schools, low rent, low income, and family affinity as factors that influenced the development in floodplains in the Lagos metropolis. Ineffective control of development and inadequate compliance with planning and building regulations were additional factors. Urban development in flood-prone areas in Lagos increased from 9.3 km2 in 1990 to 10.50 km2 in 2000 and 17.80 km2 in 2014. The study recommends that floodplains should be acquired and effectively protected to prevent any form of physical development; they should serve as natural sink for storm water and urban green for passive recreation. Urban development regulations should be strictly enforced by the relevant government agencies, such as the Lagos State Building Control Agency in the Ministry of Physical Planning and Urban Development.

Variability in Flood Sensitivity: A Household-Based Perception Study in Lagos Metropolis, Nigeria

“…These are Alimosho and Agege LGAs in the pluvial zone, Ikeja and Kosofe LGAs in the fluvial zone, and Apapa and Lagos Island in the coastal zone. Information from available studies (Wahab et al, 2014;Wahab & Ojolowo, 2018) provided the number of existing streets, flood-risk streets and buildings in the Metropolis. Using the information, a total of 512 buildings were selected based on systematic sampling for household questionnaire survey (Table 1).…”

“…Whilst flood events are evident in Nigeria, Lagos State has been the focal point of most studies (Olajuyigbe et al, 2012;Oyekale, 2013;Wahab et al, 2014;Oladele, 2018;Wahab & Ojolowo, 2018;Olanrewaju et al, 2019). The reason being that Lagos State which is a political, administrative and spatial entity in Southwestern Nigeria has been experiencing flood over the years due to natural and man-made causes .…”

“…The man-made cause pertains to increasing urbanisation in the State. High population and resulting human activities have brought about significant impact as land use/land cover change, pollution and climate change with dysfunctional effects on the ecosystem (Wahab & Ojolowo, 2018;Olanrewaju et al, 2019). Evident are wetland losses in the State due to large built up areas and activities like sea dredging; land reclamation through filling up of swamps and floodplains; and destruction of mangroves and wetlands.…”

Technical Report: Lagos floods

“…The yearly flood occurrence in Lagos is attributed to increasing development and urban expansion -encroachment on natural water channels, unregulated land reclamation and sand-filling of lagoons (Wahab and Ojolowo, 2018;Johnson, 2021) -as well as historical dredging and sea reclamation to increase the urban territory (Whiteman, 2012). As of the year 2019, the built-up areas accounted for about 50 per cent of land use in Lagos, twice as much as there was in 2000 (Figure 2) (Kasim and others, 2021).…”

Spatial knowledge and flood preparedness in Victoria Island, Lagos, Nigeria

“…The impact of the 2012 flooding was very high in terms of human, material and production losses, with 363 people being killed, 5851 injured, 3 891 314 affected and 387 153 displaced (Federal Government of Nigeria – FGN 2013 ). These flooding events have been attributed to change in climatic variables (Douglas et al 2009 ), excessive rainfall (Agbola et al 2012 ), urban development in floodplains (Adelekan 2010 ; Wahab & Ojolowo 2017 , 2018 ; Zheng & Qi 2011 ) and indiscriminate municipal solid waste disposal in water channels (Ojolowo & Wahab 2017 ). The value of destroyed physical and durable assets caused by the 2012 flooding in the most affected states of Nigeria has been estimated to be N1.48 trillion or its equivalent of $9.5 billion (FGN 2013 ).…”