**1. Introduction**

The widespread flooding in recent times, the reduction of its impacts on human populations, properties and economic activities and the impracticability of its eradication from natural environment are factors of global concerns [1–4]. In the developing countries (DCs) such as Nigeria, there is evidence to suggest that the thought of the next flooding event appears to apprehend many local communities, urban residents and authorities' hierarchy [5]. Arguably, this reality suggests among other interesting discourse, that the recognition of flooding impacts and the curiosity they drive in human populations are fundamental towards finding realistic solutions to the hazard. Worthy of note within this context is the damage

potential of flooding which is debatably unprecedented when compared to other known environmental hazards occurring within natural human environment in recent times [6, 7]. Whilst the failure and/or limitation of efforts to tackle flooding are issues in the DCs that clearly require urgent attention [8, 9], the need for sustainable development which underpins adaptability and collective resilience of the general public to flooding cannot be disregarded [10, 11].

The interplay between causes, impacts and remedies of flooding phenomenon highlights the situation in the less developed societies in respect of flooding and the risk it poses. This chapter focuses on the Lagos metropolis of Nigeria in West Africa. Under the quandary of rapid population increase and urbanization, it appears the conurbation has been subject to critical and disturbing scenarios. The idea that population growth will compel worsened future flood risk highlights the need to engage with more proactive measures of tackling flooding and more importantly more effective means of building the capacities of human population to cope with floods [11, 12]. However, present efforts at addressing the challenges of flooding in the Lagos area are flawed [13, 14]. Whilst the area signifies the economic and industrial hub of Nigeria and attracts tourists from within the country and abroad, responses to security challenges, poor corporate adaptation and resilience to flooding among other besetting environmental hazards is inadequate [15, 16]. Existing knowledge regarding particularly to the state of affairs of flooding in Lagos is unsatisfactory and falls short of solutions to the impacts of the hazard on human populations and has been unable to support sustainable development within the region [14, 17].

Within these contexts, it is imperative that the critical factors which undermine efforts at tackling flooding in Lagos as well as gaps in knowledge among other considerations which can be associated with increasing flood risk generally are identified. Thus, the need to support present efforts at tackling flooding in the Lagos region and to advance existing knowledge relating to flood risk reduction in the area motivate the debates in this chapter which considers a triplet of objectives: firstly, to summarise the widespread flooding in the Lagos metropolis of Nigeria, secondly, to summarise the current efforts towards tackling the hazard in Lagos and to identify key limitations and gaps in knowledge and practice, and finally, whilst the author argues that inadequate flood modelling in the area and limited application and scope of assessment of vulnerability to flooding undermine the success of current efforts to tackling flooding, why more of such investigations are needed is presented along with the possible challenges facing their applications in Lagos, Nigeria. It equally presents the prospects for flood risk analyses through simplified approaches and open geospatial data.

## **2. Widespread flooding in Lagos Nigeria**

Past and present flooding in Lagos Nigeria, highlight the influence of climate change, rapid population growth and urbanization on the local hydrology of the region [18–20]. First and foremost, the Lagos metropolis consists of 16 local government areas (LGAs) of varying spatial enumeration units (the largest being about 194 *km*<sup>2</sup> ) (see **Table 1** and **Figure 1**). The total land mass of the conurbation exceeds 1100 *km*<sup>2</sup> . Based on the state government's statistics [22], up to 21 million people reside in the area and this creates a yawning dimension of adverse social and environmental condition mostly overcrowding and slum development. The lack of space for a myriad of anthropogenic activities forces development of flood prone areas thus instigating a severe vulnerability to flooding for those inhabitants who lack social capacities to cope with the hazard. The abundance of impervious surfaces

**191**

**Figure 1.**

*authors.*

**Table 1.**

*Flood Risk Analysis for Critical Infrastructure Protection: Issues and Opportunities in Less…*

**S/no. LGAs Land area (***km***<sup>2</sup>**

*16 local government areas and their spatial units in the Lagos metropolis of Nigeria. Source: Adapted from [21].*

 Agege 11.263 Ajeromi-Ifeledun 12.395 Alimosho 186.195 Amuwo-Odofin 135.240 Apapa 26.798 Eti-osa 193.460 Ifako-Ijaiye 26.769 Ikeja 46.427 Kosofe 81.889 Logos-island 8.707 Lagos-mainland 19.572 Mushin 17.576 Ojo 158.884 Oshodi-Isolo 44.999 Shomolu 11.615 Surulere 23.122

**)**

in the area which generally causes increased surface water runoff and reduced soil infiltration highlights the impediments of poor urban drainage system [23].

*The Lagos metropolis of Nigeria. Inset showing the location of Lagos State in Nigeria. Source: Drafted by* 

Following the overview of Lagos metropolis presented in the preceding paragraph, a clearer picture of the devastating effects of flooding in the area can be

*DOI: http://dx.doi.org/10.5772/intechopen.95364*


*Flood Risk Analysis for Critical Infrastructure Protection: Issues and Opportunities in Less… DOI: http://dx.doi.org/10.5772/intechopen.95364*

#### **Table 1.**

*Issues on Risk Analysis for Critical Infrastructure Protection*

ment within the region [14, 17].

approaches and open geospatial data.

**2. Widespread flooding in Lagos Nigeria**

the general public to flooding cannot be disregarded [10, 11].

potential of flooding which is debatably unprecedented when compared to other known environmental hazards occurring within natural human environment in recent times [6, 7]. Whilst the failure and/or limitation of efforts to tackle flooding are issues in the DCs that clearly require urgent attention [8, 9], the need for sustainable development which underpins adaptability and collective resilience of

The interplay between causes, impacts and remedies of flooding phenomenon highlights the situation in the less developed societies in respect of flooding and the risk it poses. This chapter focuses on the Lagos metropolis of Nigeria in West Africa. Under the quandary of rapid population increase and urbanization, it appears the conurbation has been subject to critical and disturbing scenarios. The idea that population growth will compel worsened future flood risk highlights the need to engage with more proactive measures of tackling flooding and more importantly more effective means of building the capacities of human population to cope with floods [11, 12]. However, present efforts at addressing the challenges of flooding in the Lagos area are flawed [13, 14]. Whilst the area signifies the economic and industrial hub of Nigeria and attracts tourists from within the country and abroad, responses to security challenges, poor corporate adaptation and resilience to flooding among other besetting environmental hazards is inadequate [15, 16]. Existing knowledge regarding particularly to the state of affairs of flooding in Lagos is unsatisfactory and falls short of solutions to the impacts of the hazard on human populations and has been unable to support sustainable develop-

Within these contexts, it is imperative that the critical factors which undermine

Past and present flooding in Lagos Nigeria, highlight the influence of climate change, rapid population growth and urbanization on the local hydrology of the region [18–20]. First and foremost, the Lagos metropolis consists of 16 local government areas (LGAs) of varying spatial enumeration units (the largest being about

reside in the area and this creates a yawning dimension of adverse social and environmental condition mostly overcrowding and slum development. The lack of space for a myriad of anthropogenic activities forces development of flood prone areas thus instigating a severe vulnerability to flooding for those inhabitants who lack social capacities to cope with the hazard. The abundance of impervious surfaces

) (see **Table 1** and **Figure 1**). The total land mass of the conurbation exceeds

. Based on the state government's statistics [22], up to 21 million people

efforts at tackling flooding in Lagos as well as gaps in knowledge among other considerations which can be associated with increasing flood risk generally are identified. Thus, the need to support present efforts at tackling flooding in the Lagos region and to advance existing knowledge relating to flood risk reduction in the area motivate the debates in this chapter which considers a triplet of objectives: firstly, to summarise the widespread flooding in the Lagos metropolis of Nigeria, secondly, to summarise the current efforts towards tackling the hazard in Lagos and to identify key limitations and gaps in knowledge and practice, and finally, whilst the author argues that inadequate flood modelling in the area and limited application and scope of assessment of vulnerability to flooding undermine the success of current efforts to tackling flooding, why more of such investigations are needed is presented along with the possible challenges facing their applications in Lagos, Nigeria. It equally presents the prospects for flood risk analyses through simplified

**190**

194 *km*<sup>2</sup>

1100 *km*<sup>2</sup>

*16 local government areas and their spatial units in the Lagos metropolis of Nigeria. Source: Adapted from [21].*

#### **Figure 1.**

*The Lagos metropolis of Nigeria. Inset showing the location of Lagos State in Nigeria. Source: Drafted by authors.*

in the area which generally causes increased surface water runoff and reduced soil infiltration highlights the impediments of poor urban drainage system [23].

Following the overview of Lagos metropolis presented in the preceding paragraph, a clearer picture of the devastating effects of flooding in the area can be

#### **Figure 2.**

*Examples of flooding scenes in the Lagos metropolis of Nigeria: (a) living room submerged by flood water, (b) residential building submerged, (c) local community affected by flood waters, and (d) expressway overwhelmed by flood water. Source: Online images of flooding in Lagos, Nigeria.*

appreciated. Typically, the hazard which has been generally attributed to climate change and poor urban planning affects hundreds of thousands of people (mostly through homelessness, physical injuries, mortality, spread of diseases and emotional trauma), destroys chains of urban infrastructure and disrupts economic activities [14, 24]. Fiscal losses caused by the hazard in the area amount to millions of US dollars [25]. Although fluvial and coastal flooding occurred in the early days of flooding – i.e. in the early 1960s – pluvial floods resulting from prolonged rainfall which overwhelms urban drainage facilities and soil infiltration capacity are now more widespread. Such floods usually recur annually between the months of March and October (but usually more severe in July) with considerable environmental and socio-economic impacts [26]. These floods which have triggered concerns for environmental mismanagement, urgent humanitarian needs and services, primary health delivery, solid waste management, urban development and governance, and the resilience of the general public within the area are claimed to be more severe for Lagos Island, Apapa, Ikeja, Mushin, Surulere and parts of Ikorodu [16, 26–29]. The magnitude of flooding experience in the Lagos region of Nigeria is highlighted in **Figure 2(a-d)** below. A typical example of flooding event in Lagos is the July 2011 flooding, caused by a heavy rainfall that lasted 17 hours. The flood affected more than 10 thousand people with deaths exceeding 100 and a range of damage including public infrastructure such as roads, bridges and schools. Houses were submerged by flood water while lots of properties including vehicles were destroyed due to the intensity of the flood. An estimated economic loss of about 50 billion Naira (\$US 320 million) was incurred [30].
