Flood-related challenges and impacts within coastal informal settlements: a case from LAGOS, NIGERIA

ABSTRACT This study considers climate impacts and environmental challenges (flooding and sea-level rise) in one of the coastal informal settlements in Lagos, Nigeria. A mix of methods was used to generate data. First, 14 residents, selected through purposive sampling, were interviewed. A survey (sample size = 300) of residents was conducted as a follow-up to the interviews. To elicit information on spatio-temporal dimensions, GIS-based mapping showed change in land use/cover from 1990 to 2020 and simulates impacts with 0.5 m, 1 m, 1.5 m and 2 m sea level rise scenarios. The results illuminate negative corollaries at the intersection of informal urbanisation and climate change in coastal settings. Flood-related impacts on the built and natural environment were significant. Climate adaption and resilience will need to involve restoring the decimated natural ecosystem and integration of indigenous systems in the study area and similar low-income coastal urban communities.


Introduction
Growing utilisation of the coastal zone, through urbanisation, has resulted in increasing coastal risk and vulnerabilities, especially in areas regarded as slums and informal settlements in cities within sub-Saharan Africa (SSA) and beyond (Sterzel et al., 2202).The fact that 'greater vulnerabilities arise in coastal settlements with higher inequalities' is affirmed in the latest IPCC report on 'Cities and Settlements by the Sea' (Glavovic et al. 2022(Glavovic et al. , p. 2169)).Estimates show that over 50% of urban residents in SSA live in these areas, and a significant number are located on the waterfronts, low-lying areas and riparian corridors in coastal cities (Satterthwaite et al. 2018).Compared with other categories of urban residents, poor households within slums and informal settlements are generally more exposed to impacts of climate events and other environmental challenges (IPCC 2012).This is the situation in Lagos, with its over 100 slums and informal settlements.Most of these are located within the city's coastal zone stretch, where water-related environmental challenges are common experience and projections in sea level rise a concern for the future.
Climate adaptation initiatives need to engage the informal and low-income sector in cities. Poor documentation on informal socio-ecological processes within the low-income urban context is detrimental.Hence, the motivation to consider past, present and future climate impacts and environmental problems within slums and informal settlements in coastal areas (Bai et al. 2018).Understanding the current and future impacts is crucial to chart adaptation pathways.
This article focuses on climate impacts and environmental challenges (flooding and sea-level rise) in one of the coastal informal settlements in Lagos, Nigeria.It is guided by question -how has and/or will flooding and sea-level rise impact people, the natural and built environment in Idi-Araba community?The study's originality lies in presenting causes and impacts of flooding from the residents' account and experience, as well as utilising a spatio-temporal dimension through consideration of land use changes over time and future sea-level rise scenarios.This article aims to draw attention to past, present and future neighbourhood-level impacts that inform locally-appropriate adaptation initiatives in the case community and similar low-income urban coastal communities across developing countries.

Climate impacts, flooding and informal urban settlements
Climate and environmental challenges within cities in developing countries, Lagos inclusive, have been addressed by many scholars.Flooding (both fluvial and pluvial) is a notable challenge for coastal cities and is usually linked to current and projected rise in the sea level (Moftakhari et al. 2018).The problematic impacts of flooding and sea-level rise on urban residents are well documented, through journalistic productions and academic publications, although peer-reviewed evidence from the African context is lower compared with, for instance, studies emanating from Asia.Studies by Atufu and Holt (2018), Lucas (2021) provide recent examples that demonstrate these impacts at the city-wide scale in Lagos.Specifically, pluvial flooding in Lagos alone have affected over 26 hectares of land and resulted in over $103 million economic losses (Croitoru et al. 2020).Other coastal cities in Africa have similar experiences.Amoako's 2016) and Udelsmann Rodrigues' (2019) studies on low-income low-lying urban communities in Accra and Luanda respectively highlights same impacts as identified in Lagos.
On the other hand, a few positive impacts were explained in some literature.Available instances are people offering for-fee commuting assistance during flooding (Odunuga et al. 2012) or patent medicine sellers who make more sales after flooding (Lawanson and Odunbaku 2017).These are however trivial when viewed alongside overwhelmingly negative impacts.
The focus on slums and informal settlements in coastal locations is relevant.Climate change leads to SLR and increase in flooding within the usually ecologically fragile coastal zone location of slums and informal settlements.Apart from sea-level rise and changing rainfall patterns, flooding within slums and informal settlements can be linked to absence of infrastructure such as drainage, inadequate services such as waste collection, poor quality housing (substandard walling materials, flimsy roofing systems etc.) (Ajibade et al. 2015;Adedayo and Malik 2016).Due to the weak socio-economic situations in these coastal informal neighourhoods, impacts of flooding and SLR are usually significant (Adelekan 2010).
Table 1 captures impacts that are peculiar to slums and informal settlements, as identified in relevant local and international studies.Olanrewaju et al. (2019) highlights health implications of flooding in poor urban communities such as Ajegunle, Lagos.Since, floodwater come with debris, faecal pathogens and pollutants; in the absence of drainage infrastructure and clean portable drinking water, illnesses are usually inevitable.Flooding often leads to waterborne diseases such as leptospirosis, cholera, diarrhoea, rotavirus, typhoid, malaria.Within studies conducted at different times across different informal settlement locations in Lagos (Ajibade and McBean 2014;Olajide and Lawanson 2014;Abiodun 2021), not less than 88% of the survey respondents have experienced damage to properties from flooding.In Makoko settlement, a barber lost his equipment and entire business to flooding (Lawanson and Odunbaku 2017), while in Ijora-Badia settlement parents reported that their children cannot attend school when the roads are inundated with floodwaters (Olajide and Lawanson 2014).Sea-level rise is already a reality in Lagos and other coastal cities in Africa.For Lagos, annual 0.075 km 2 inundation rate was identified by Fashae and Onafeso (2011), and it does not appear this rate has slowed down.It is resulting in consistent loss of built-up areas into the ocean.In the Dansoman coastal area of Accra, ongoing rate on coastal inundation due to sea-level rise, is projected to result in loss of about 381 and 926 buildings by 2050 and 2100 respectively (Appeaning Addo et al. 2011). Nyadzi et al.'s (2020) review shows that quantitative projections of SLR impacts on land, buildings and the built environment in West Africa coastal regions are inadequate.This knowledge gap, in light of expected changes, shows that better attention must be paid to future flooding impacts within slums and informal settlements.It is necessary to provide information on the dimensions and magnitude of future impacts, given different SLR projections.This can inform flood risk management, resilience and climate adaptation strategies.

Study area and methodology
Lagos, a coastal city located within latitudes 6 °23′N and 6 °41′N and longitudes 2 °42′E and 3 °42′E, contains approximately 20 million people.It is exposed to frequent and intense rainfall, storm surges, coastal flooding with predictions of sea-level rise (SLR).In a 2007 study that has not been updated, Lagos ranked fifteenth globally for exposed population to flooding based on projections of the 2070 climate scenario (Nicholls et al. 2007).This poses serious risks to infrastructure, housing, and the lives of around 6 millionmostly living in slums and informal settlements along the coastal areas in Lagos (Ajibade et al. 2016).Idi-Araba is one of the coastal informal communities within Oworonshoki area of Lagos.It started as a fishing settlement from the early 1980s.The community was named after a big tree which then served as a meeting point for fishermen to socialise, cook and sleep (Olorunwa 2014).
Idi-Araba community contains around 2456 persons, fairly split across the male and female gender, belonging to 709 households.The residents are majorly of the Ilaje ethnic extraction, although other Nigerian ethnic groups are present.Migrants from Togo, Benin, Niger and Ghana also live there (Lagos Urban Studies Group 2019).A 2015 assessment shows that 88% of residents are in the 21-40 age group, 67% are self-employed in the informal sector, while 67% have a least junior secondary education (Lagos State Government 2015).

i) Semi-structured interviews
This study explored verbal communicative strategies of the residents to collect data through semistructured interviews.Fourteen residents, selected through purposive sampling, were interviewed.The criterion is that they had lived for at least 12 years within the community.The length of residency is to ensure that interviewees' comments on climate and environment-related issues are experiential.The interviews were framed around a set of predetermined questions although other questions emerged from the dialogue, following Whiting (2008).The interview questions sought to elicit information on the residents' experience on climate-related impacts (focus on flooding and sea-level rise) and related environmental challenges within the community.
After selection, a potential interviewee was informed about the research objective and expected questions.A verbal consent to voluntarily participate and be recorded is given before interviewing commenced.All the interviews, except one (in which the interviewee withheld permission), were audiorecorded.The audio recordings were later transcribed and where relevant translated.Most of the interviews were conducted in the vernacular language (which the researcher speaks and understands) using easily understood terminologies that best convey what is intended.The interviews took place between November 2019 and March 2020.

Ii) Survey
A survey of residents was conducted as follow-up on the interviews.In line with the research objective, the survey focused on climate impacts (flooding and SLR) and other environmental challenges within the community.Earlier engagements with residents through semi-structured interviews and review of literature informed design of the questionnaire (survey instrument).Using the sample size determination formula by Krejcie and Morgan (1970) (See equation 1), a sample size of 333 was determined from the 2456 estimate population in Idi-Araba settlement, at 95% confidence interval and 5% error margin.The sample size was then scaled down to 300, given the time and resource constraints.
A group of five literate residents were trained to assist with administering the 300 questionnaires to randomly sampled residents within the community.The assistants are familiar with the area and fluent in English and the vernacular language.They completed each questionnaire by interviewing the randomly selected respondents.In some cases, when residents were busy at home or business location, they dropped the questionnaire and returned to retrieve it when a respondent wants to selfcomplete the survey.Of the 300 questionnaires produced and given out to the assistants, 270 were retrieved.Upon screening of the retrieved questionnaires, only 247 were used for analysis.Questionnaires with more than three incomplete sections were excluded from the analysis.

iii) Mapping
To elicit information on spatio-temporality of environment and climate issues, GIS-mapping of Idi-Araba was done.The goals were to show change in land use/cover from 1990 to 2020 and simulate impacts with 0.5 m, 1 m, 1.5 m and 2 m SLR scenarios.The process started by using ArcGIS software for delineation and digitising the settlement's boundary and features such as such as water bodies, vegetations, roads and buildings.Historical satellite imageries (Landsat) obtained from the United States Geological Survey (USGS) were used for temporal analysis of land use/cover changes.The study area's boundary and features were overlaid on the historical Landsat imageries for 1990 and 2020.This involved 'extracting by mask' using the Spatial Analyst tool in ArcGIS to ensure the existing conditions are contained in the digitised map which was then overlaid on the historical Landsat and SENTINEL imageries.It used the supervised maximum likelihood classification for image analysis in ArcGIS 10.5 to determine changes in the land use/land cover over the specified years.
For the SLR scenarios and impacts, Advanced Land Observing Satellite (ALOS) digital elevation model (DEM) with a resolution of 12 m was obtained.With the aid of ArcGIS, land extent, vegetation, water bodies and structures within the study area was overlaid on inundation zones projected for 0.5 m, 1 m, 1.5 m and 2 m SLR scenarios.Grids of the ALOS DEM supported with SENTINEL imagery data were imported into ArcGIS.The mosaic function was applied to merge the DEM grids into a seamless raster.Inundation zones derived from the DEM and raster were overlaid on the delineated coastal extent to extract vulnerable regions to different SLR scenarios.Inundation estimates for land extents were derived by overlaying the inundation zones with the appropriate exposure surface dataset.For buildings, estimating the effect for the different SLR scenarios was done through a query dialogue ('select by location' tool) that selected all buildings within the extent SLR impact, combining it with 'Intersect Overlay' tool to create polygon feature of the buildings affected.Maps were created to reveal the extent of the land use/land cover change and SLR scenarios.Table 4 quantitatively summarises the maps generated for the different SLR scenarios.

Residents' and housing characteristics
Information about the demographic composition, socio-economic characteristics, service availability and housing situation within the community are provided in Table 1.Of the 247 respondents, 53% were male, 47% female, and 75% are within working age groups -between 25 and 60 years.Most (at 48.8%) are self-employed.Only 13.7% had no form of formal education.Landlords represent 37.1% of the respondents while 35.9% are renters.In terms of services, 68.1% of houses are connected to electricity, while others are not.About one-third each are connected to water from pipe-borne municipal (33.1%) and community borehole (31.5%) sources.For sanitation, majority use water closet either within (30.2%) or outside the house (43.1%).Open defaecation is still practiced by some 6% of the residents.
Material composition of the respondents' dwellings were investigated and reported in Table 2.This is important because materials that buildings are made from and their construction techniques affect their ability to prevent, withstand or give in to flooding impacts.Houses in the community are majorly (over 70%) walled with sandcrete blocks, which is the conventional building material in Nigeria.The blocks are of questionable quality, given that they are easily negatively impacted by agents of weathering.Roofs are mostly covered with aluminium sheets.Only 9.3% of the houses do not have any form of ceiling.A variety of floor finishes are available.Floors with cement mortar (26.6%) have the highest percentage, followed by those covered with rug (19.0%).

The settlement's evolution, land use change and sea-level rise implications
As earlier stated, the Idi-Araba community started as fishing settlement, populated by people who work as fishermen.'The main occupation of Ilaje people is fishing, so majority initially moved to this neighbourhood for fishing.We live and work close to the coast', an elderly resident explained (Interview 4, November 2019).The ilaje people live in stilt houses on waterbodies in rural coastal areas of Ondo State.They have strong affinity to the coastal environment for livelihood activities such as fishing.As a result, 'living in any water-logged environment is not a problem to an Ilaje man' (Interview 13, February 2020), 'particularly those of us born on the sea at Ilaje in Ondo state.We are used to the weather.There is no sea that can threaten us in Lagos' (Interview 4, November 2019), two male interviewees explained.
At onset, the waterfront settings in Idi-Araba had wetlands, trees and other water-linked ecological features (see Figure 1).Most houses were therefore built on stilts in the swampy areas.The demand for land for terrestrial housing development, a departure from the aquatic living, has significantly changed situation.A personal account shows how transformation typically took place.A resident explained that 'the place was covered by the sea in 2001.It got to the navel, it's up to 4 or 5 feet when we entered it . . .I was the one that later filled it, with human effort.We initially built with plank on the river, we [later] bought sand and filled the river to form an island so that we can build on it' (Interview 4, November 2019).This is 'applicable  to everybody from the slope down here.Everyone filled his/her space.We had to fill this place because cost of land here was then cheaper than buying in the upland' (Interview 4, November 2019).
The exploitation of available vegetation for housing construction is noteworthy.A female resident who had lived for over 30 years report that 'this place was all groove before.There were many big trees, we used some of the trees to build' (Interview 1, November 2019).A related account by someone who had lived there from 1992 is that 'most of these places were bushy mangrove area.Now those things are not there again, houses have occupied everywhere.We cut them [vegetation] and fill up the area' (Interview 10, December 2019).Corroborating this, another resident said 'before there were different species of big trees.But we burn them and fill those places when we bought it . . .The late Baba that sold the land to us instructed us to start developing immediately, that we must not delay, that we should develop it on time.We built the timber house on it, after that we started filling the land' (Interview 6, November 2019).
The measure of land cover changes, shown in Figure 1, aligns with the residents' account.The percentage of built-up area went from 27.5% to 70.6%, almost tripling between 1990 and 2020.It significantly took up the wetland, which was reduced to less than 10% coverage from a 50.9% coverage in 1990.The percentage of vegetated land cover remained the same, at 21.6%, but the areas where they are present changed.Vegetation within the now built-up area largely disappeared.The only vegetated land cover captured for 2020 are swamp areas often covered with water hyacinth, an invasive aquatic plant (see Figure 2).
Given the land use changes recorded and projections in sea-level rise, flooding and the impacts of land and buildings will continue in Idi-Araba.Through four SLR scenarios modelled for the settlement, the extent of building, roads and land areas that will be affected in Idi-Araba were revealed.A summary of the extents is presented in Table 3, while the mapping is available in the appendix.As might be expected, higher sealevel rise means more land area, buildings, and roads will be negatively affected by water inundation.For instance, over 75% of land in the community will be lost, 903 buildings will be affected, and 32 streets submerged with 2 m rise in the sea level.

Perceptions of climate change and associated corollaries
The residents understand climate and environmental issues through what is referred to as 'the knowledge we gained from our fathers . . .using local knowledge, inherited knowledge, knowledge from experience' (Interview 4, November 2019).They primarily rely on what is learnt and experienced over the years -indigenous knowledge systems -to understand the weather, seasons, and the evolving climate variability.Literate residents at times follow weather forecast from meteorological authorities.An overwhelming majority believe there is climate change/variability, especially manifesting through change in rainfall patterns.Figure 3 shows the residents' perception, as captured through the survey.Most agree that increased rainfall, higher average temperature and sea-level rise are attributable to climate change.
Notwithstanding the agreement by most residents, a few persons do not believe there is climate change.An elderly man who has lived in the settlement for 20 years thinks 'it [the climate] is not changing because it has been the way it used to be' (Interview 6, November 2019).Providing a religious dimension for his climate change denial, though confirming the occurrence of extreme weather events, he said 'we are now approaching end of the world.All those breezes blowing, coupled with the hot weather, and everything that affects people, fishes and animals were caused by our sins.It's better for us to start asking for God's forgiveness' (Interview 6, November 2019).
The changing climate is further established through the 2019 rainy season, which was seen as a departure from the past.The residents admit that the 2019 rains 'weren't like that before.It's now that the rain has no season and duration.Rain now falls anytime' (Interview 5, November 2019); 'the kind of rain which fell this year has not been experienced for the past 12 years.This year's rain is very serious' (Interview 6, November 2019); 'this year's rain was very much.We have entered December and the rain has not stopped' (Interview 9, December 2019).A more direct explanation is that 'years back, rain normally falls between February and July.But now we are still in the rainy season . . .We are in November, the rain is still falling . . .That is why we said there is climate change' (Interview 3, November 2019).
The 2019 rainfall pattern in Lagos was indeed unique.Rather than peak in June, as observed between 1960 and 2010 (Sojobi et al. 2016), meteorological measurements show that rainfall peaked with an unusual monthly cumulative of 929.7 mm in October in 2019 and continued significantly into November.
A notable flooding pattern was reported in the settlement.Almost all the interviewees observed that a periodic severe flooding cycle usually accompanies the raining season every 3 to 4 years.'We have been studying how the water comes . . .how it comes periodically . . .We usually experience it every three years.But this year's flood was so much.More than we've ever experienced every three years', a female resident explained (Interview 1, November 2019).Further capturing the phenomenon is the explanation that 'the rain that falls every three years affects us.It has been like that since I got to this place [24 years ago].It comes in large quantity every three yearscovering everywhere and entering houses' (Interview 12, December 2019).
The scientific principle underscoring the observed 3-to-4-year flooding phenomena within the settlement deserves to be unravelled.Based on literature accessed, it might be linked to Sojobi et al.'s (2016, p. 556) claim that Lagos experiences 'extreme and high variable rainfalls, which are associated with the increased warming trend, [in] periodicities of 1 to 3 years with a probability of 86.45% of occurring every 3 years between April and September'.Notwithstanding this explanation, additional evidence would be useful to demystify this phenomenon.

Impacts of flooding on built environment in the settlement
Flooding significantly impacts the community -the people (residents) and place -natural and built environment, including buildings, roads, and other available infrastructure.These affect livelihoods, health and well-being, and other aspects of life.Not only that 'when it rains, our road becomes difficult to ply because the road is not tarred' (Interview 9, December 2019), in many situations, floodwaters enter the buildings.From the survey, 42.7% of respondents have had their houses affected by flooding and sea-level rise.For the impacted buildings, damage ranges from sinking foundation (23.9%), damaged furniture (19.1%), damage to walls (16.4%), defects in sub-structure (12.5%) (See Figure 4).Only 2.1% of respondents reported building collapse.
Flooding affects houses such that 'in some places, the water gets to the window level' and 'when it penetrates the building blocks, they become weak and thereby break away' (Interview 1, November 2019).A personal account, reflecting the common experience is that: 'buildings normally sink, some collapse, some go down because of water that comes around.Water doesn't go, it will just occupy the whole place for about almost 3-4 months before it finally dries . . .I've experienced it before.My documents, the one I used for my education, my folder, everything just spoilt . . . .The water came in the night, which I didn't expect.Before I could evacuate my family, it has messed up the whole house.I found it difficult to take my things because of the high water level.I had to leave the documents for two months.Before I came back, water has spoilt everything' (Interview 3, November 2019).
In some instances, the impacts affected rent paid by tenants, either increasing or decreasing it.A total of 72 respondents (29.6%) acknowledged that flooding and sea-level rise affected the amount of rent paid.Of those respondents affected, 47% had reduced rent while 45% had to pay a higher rent.No rent change difference was noted across genders, based on analysis conducted.A houseowner explained that rent reduces because when it floods 'the landlord normally stays, but tenants leave.They don't come back, that is why we have cheap rent, the house rent here is cheaper than the high side' (Interview 3, November 2019).Heavy rainfalls, which lead to flooding, are most times accompanied by windstorm which also affect buildings and infrastructure.It was reported that 'breeze destroyed a woman's house.It damaged six buildings on this street.On the other street, two electric poles were removed.One pole fell on a popular man in his house and killed him.The other pole also fell but did not affect anyone' (Interview 6, November 2019).Explaining how the damage could have been prevented, a resident explained that 'when I came in here, there are trees that absorb some of the forces of wind.Now, there are no more trees here.I remember there was heavy wind that destroyed houses, electricity poles and stuffs like that . . .assuming those trees were there, maybe they would have absorbed some forces of the wind' (Interview 10, December 2019).
Poor housing construction makes impacts of flooding and windstorm stronger.The understanding is that windstorm 'affects houses when they are not well built, and when people don't have money to maintain their house' (Interview 7, November 2019).It was also noted that 'when a building is faulty and breeze blows on it, or someone had constructed his building without pillar [columns] or any other supporting structure -the breeze can pull it down' (Interview 5, November 2019).
Apart from houses and the built environment, flooding disrupts the people's lives and livelihoods.Since some 'had to be removing water for like two to three days . . .It affects people's work because it hinders them from going out' (Interview 6, November 2019).It affects health, notably because 'this water [runoff] usually eat [infect] people foot', referred to as 'jomijomi' in the local language (Interview 1, November 2019).This is medical condition known as athlete's foot disease, a contagious fungal infection.Flooding affects agricultural cultivation.For example, someone 'planted corn, vegetable, but when the flood came it was all destroyed' (Interview 2, November 2019).

Discussion
The withstand the repeated impacts of flooding.The kind of sandcrete blocks used becomes weak when exposed to persistent flooding (Odeyemi et al. 2018).
All the flood-related problems -damage to property, disruption of livelihoods, health challenges etc., have most likely aggravated over the years.These impacts show the absence of flood risk management.While the Lagos state government seems to have made some structural and non-structural flood risk management strategies (Adelekan 2016;Lucas 2021), these appear to largely exclude slums and other lowincome and informal areas.
The emergence and growth of Idi-Araba is informaltypical for slums and informal settlements in Lagos and African cities generally.This case settlement shows the implications of informal urbanisation on the natural environment.Through their work within Badia community in Lagos, Ajibade and McBean (2014), explain the phenomenon -that these communities encroach hazardous landscapes and engage in environmentally intolerable activities, which undermine biophysical integrity and erode natural prevention for flooding.Some scholars have touted urban informality as proenvironmental, in terms of resourcefulness, selfreliance and adaptability to environmental stress (Benson 2014) and locational characteristic which presents opportunity for green infrastructure (Adegun 2017).But the trajectory within Idi-Araba settlement shows that informal mode of urbanisation may rarely be beneficial environmentally.The progressive decimation of natural ecosystem and the subsequent reduced capacity to adapt to climate and environmental impacts poignantly illustrate this downside.Decimation of the natural ecosystem leads to loss of ecosystem services giving room for flooding problems and making sea level rise more impacting.
Decimation of natural ecosystems shows the need for ecosystem restoration.Idi-Araba settlement, and other urban settlements along the West African coast, are suitable sites for the implementation of naturebased solution.A good situation is the tree-planting to restore and improve mangrove cover, as examples from within informal settlements in Nairobi, Kenya (Mulligan et al. 2020) and Windoek, Namibia (Thorn et al. 2021) show.This approach has advantages of cost-effectiveness, economic, ecological and health co-benefits.It will demand partnership with civil society and participatory community-involved approach -a character which can be harnessed in Idi-Araba and most informal settlements.
The utilisation of indigenous knowledge systems within the community can be incorporated into adaptation strategies and nature-based solutions to prevent and reduce flooding impacts.Integration of indigenous knowledge systems into flood management strategies in coastal areas have been recognised and advocated by scholars such as Obi et al. (2021) and Fabiyi and Oloukoi (2013).

Conclusion
Through the case study of Idi-Araba settlement in Lagos, Nigeria, this study has shown what happens at the intersection of informal urbanisation and climate change.Flooding and other environmental challenges manifest, and they impact people, the built and natural environment.These impacts would most likely continue, within informally developed urban neighbourhoods in coastal zones.Having drawn attention to the impacts of flooding, this study advocates for locallyappropriate adaptation strategies.Indigenous knowledge systems and community social capital can be harnessed.Nature-based solutions are a veritable means and can be incorporated into informal settlement upgrading initiatives for resilience to flooding, sea-level rise and other environmental challenges.
The state's absence in evolution of the case study community cannot be dismissed.This absence.Though not new, is of course not plausible.Rather than 'being absent through their inaction in informal growth in flood-risk areas' (Amoako 2016, p. 5), the state has a key role to play in redeeming this situation of perennial flooding and projected sea-level rise in coastal zone informal settlements.Sweden (2018), and Visiting Scholar at the Canada Centre for Architecture, Montreal (2016).Dr Adegun´s main scholarly interests focus on environmental sustainability in urban areas of Nigeria and other parts of sub-Saharan Africa, especially with respect to low-income housing, such as slums and informal settlements.His recent works have been supported through the Climate Research for Development (CR4D) Programme, Africa Academy of Sciences (AAS) and DAAD ClimapAfrica Programme.

Figure 1 .
Figure 1.Analysis of land use cover change within Idi-Araba between 1990 and 2020.

Figure 3 .
Figure 3. Residents' perceptions on Climate change, rainfall patterns and sea level rise.

Table 1 .
Flooding impacts within slums and informal settlements in Lagos.

Table 2 .
Socio-demographic profile and housing characteristic.

Table 3 .
Dwelling characteristics of the respondents.

Table 4 .
Sea-level rise impacts on buildings and roads in Idi-Araba.
impacts of flooding identified in this study resemble what earlier studies have found (See for example Adelekan 2010; Ajibade and McBean 2014; Abiodun 2021).The projected impacts of SLR scenarios on buildings aligns with what Appeaning Addo et al. (2011) projected for a coastal settlement in Accra.The poor quality of materials used in housing construction not only makes the dwellings vulnerable, some houses collapsed because they cannot Figure 4. Flooding Impacts on buildings/built environment in the settlement.