Flood and its socio-economic implications on man and its environment

Introduction

Flooding remains the most frequently reported costliest disaster worldwide, accounting for over 40% of natural worldwide disaster (Tapsell and Tunstall, 2007). It is in fact the most common of all environmental hazards and it regularly claims over 20,000 lives per year and affects around 75 million people worldwide (Smith, 2006). Floods cause about one third of all damages from natural disaster (Akin, 2009).

Flood is a body of water which rises to overflow land, which is normally submerged [National Environmental Survey/Action Team, (NEST), 2011]. They are environmental hazards that occur regularly every year in different parts of the country especially during the rainy season. Flood water overflow expanse of land, submerging the land. Flood occurrence is usually due to the increase in the volume of water within the water body such as rivers and lakes. This causes water to exceed the drainage channel capacity and overflow its bounds.

Flooding occurs also when excess runoff is created owing to the inability of the soil to infiltrate water or when the soil has reached its field capacity or saturation. The result is excess runoff which submerges the landscape. This form of flooding is particularly the case in most urban centres of the world and Nigeria in particular, where urbanization has disturbed or altered the natural process of infiltration.

In many urban centres in the country, the dry season brings joy and relief even when the taps are dry, while the rainy season spells agonizing discomfort and the fight to keep life and property from flood devastation. In urban centres in the country, especially in the flood prone coastal areas of the country, floods has posed serious threat to life and property and rendered thousands of people homeless (National Technical Committee on Water, 2008).

The general effect of flooding is very intense both in magnitude and impact. Its occurrence has constantly affected the health, reduced land use and property value while the cost of living is in persistent rise. The impact of floods in our environment can be viewed from three different perspectives; its impact on the man, the natural environment on and its impact on the built or artificial environment.

Definition of flooding

Flood, according to Resonzweig (2009) can be defined as an unusual accumulation of water above the ground, which is caused by high tides, heavy rainfall, or rapid run off from paved surfaces. Some rivers are known to have natural flood plains. The most serious floods occur along coastal areas. In these areas, heavy rainfall and poor soil combine to cause flooding.

Burrus (2010) defined floods as when more water is brought into drainage channel than the channel can carry. The excess overflow the banks and spread out to the surrounding lands, producing the flood condition (flooding). Flood is any overland flow over urban land sufficient to cause significant property damage, traffic obstruction, nuisance and health hazards which include river flood, flash flood and damages (Hendrick, 2007)

U.N. Hydrologists Wisler and Brater (2009) viewed flood as extreme hydrological event which occur when the infiltration capacity of the soil is lower than rainfall intensity. Rain water reaches the surface of the earth, percolates into the ground to form part of the shallow sub-surface flow and saturation overland as well as ground water flow.

Due to the nature of flood occurrence, the full analysis of the effect of the flood requires us to link the physical hazard to the health and socio-economic impact resulting from them. It is believed that the most proper evaluation of effect of any environmental problem including flooding will involve assessing physical hazard to acquire their impact in the health and socio-economic terms.

Characteristics of floods

Gabler (2010) shows that there are several factor used to describe the extent and nature of floods. For instance, its duration, area of coverage, velocity of flow, and volume of water discharged per unit time.

However, these factor are generally affected by amount of precipitation, seasonality (season of the year), Nature of the soil, Nature of slope as well as the geomorphic characteristics of the area.

The most important characteristics of flooding according to Akin (2009) are;

  1. Flood duration: Flood duration refers to the length of time which an area is under peak water discharge or runoff. Some floods are known to rise and recede within an hour. While other flood areas remain at thigh stage for several days, especially in the rainy season at the coastal areas. A flood hydrograph shows the continuous trace of discharge against time during a flood event.
  2. Flood frequency: Flood frequency is a statistical measure of probable occurrence of flood of a given magnitude. Magnitude of every flood is defined by its frequency. Large flood occurrences are relatively infrequent and they have long reoccurrence intervals of perhaps about ten years. On the other hand, small floods occur more frequently at least about four times yearly having a small return period or reoccurrence period.
  3. Flood seasonality: This is a measure of any seasonal nature of flood of any magnitude. Floods are most common in rainy or wet seasons especially in the tropical regions of the world. This is so because large rivers are known to attain their peak flow during the rainy season while conventional rainfalls can also cause streams to flood.
  4. Flood velocity: Flood velocity is the speed at which flood water moves. It is usually ascertained by measuring the distance of the flood water flow compared to the time duration of flow. Flood velocity is usually by the nature of the area.

Causes of flooding

Flood is generally caused as a result of many conditions working singly and in synergy. These conditions are mainly natural and anthropogenic in nature. Natural causes of flooding are enhanced mostly by nature of weather and landscape, while anthropogenic causes of flooding are enhanced by human activities (Oriola, 2008).

Hoyt (2009) however suggested that flood are natural events and that man does not create floods, though his actions in deforestation and urbanization especially in flood prone areas, has increased flood occurrences in the world.

“Thus in real sense, the flood problem is caused by people. If man had left the flood prone areas, there would have been no flood damages and problem and hence, flood would have been perceived as Natural Phenomena rather than a Natural Disaster”.

Wright (2011) stated that we appear to be making the problem worse by creating artificial conditions that produce excessive runoff which is the most common cause of flood. Man’s activities in replacing natural soils and rocks which absorb water like sponge, with structures of concrete and asphalt which cannot absorb or infiltrate water into the ground water.

General causes of flooding according to Wright (2011) include;

  1. Heavy rainfall: Heavy rainfall is experienced in some parts of the world especially in the tropical regions. This region is found within latitude 00 to 300 North and South of the equator. Rainfall intensity is very high in this region averaging about 2000mm annually. This intense rainfall is most prevalent in the rainy or wet season of the year from March to September. Heavy rainfall makes it difficult for most soils in the tropics to infiltrate rain water at the rate of rainfall intensity. The situation is further worsened by the amount of paved surfaces that characterize our urban environment which also frustrates infiltration of rain water.
  2. Soil nature: The nature of the soil through which rain water flows or percolates, determines to a great extent the rate of infiltration and the volume of water that will be generated as run-off. Most soils have high infiltration capacity others have low infiltration capacity. Research shows that an average soil in West Africa reaches saturation at soil moisture storage of 200mm. this saturation is achieved mostly in September in Nigeria. This assertion implies that most parts of the Nigeria landscape especially the low relief areas are liable to flooding in September which is the peak of the rainy season.
  3. Deforestation: Large scale deforestation in the forest and vegetations of the world has helped to increase the flood occurrence. This is statement is made in light of the fact that forest and vegetations hold back direct rain water and release it gradually to the soil such that rainfall intensity can match the rate of infiltration. This enables proper infiltration to be achieved, discouraging flooding. High infiltration is usually maintained in the forest areas, hence removing trees and vegetations without replanting or even exploiting them in manner which out-matches its replacement or replenishment would create more floods in the world.
  4. Climate change: Change in our climates has also exacerbated the occurrence of floods in the world. Climate is a vital environmental factor that shapes and reshapes various human activities (Etuonovbe 2011). The United National Framework Convention on Climate Change (UNFCCC) (2008) define climate change as change in the climate which is attributed directly or in directly to human activities that alter the composition of the global atmosphere and which increases climate variability observed over a comparable time period. The National Emergency Management Agency (NEMA) (2012), attributed climate change to the worst flood disaster witnessed in the country in 2012. Climate change acts indirectly to aggravate urban flooding by altering pattern of flooding in flood prone areas, thereby frustrating efforts of flood prediction (Odjugo, 2012).
  5. Poor waste disposal: Poor waste disposal especially in our urban centres cause blockage of drainage channels. These channels which are supposed to allow free flow of water are blocked with debris and most times refuse and sewages. These substances increase the bed load of the drainage channels and rivers causing them to rise. The result is rivers overflowing its bounds into adjourning flood plains. Bridges and dams are also constructed across rivers and this obstructs river flow and cause occasional flash floods (Akin, 2009).
  6. Poor land use policy planning and management: Poor land use policy planning and management constitute a major problem to urban flooding in the world especially in the developing countries of the world. Land use policies and adequate planning which should ensure proper sitting of buildings, structures, road construction, drainage construction and land use ordering, is seriously lacking in the developing nations (Gabler, 2010). It is unavailability of these control tools that have permitted the uncontrolled development as witnessed in the developing nations of the world. It is unfortunate to note the inability of most developing countries like Nigeria to properly plan and order use of land which has at least promoted the occurrence of flooding or failed to control it. (Efe, 2010).

Flood prediction

The prediction and forecast of floods depends greatly on the consistency of available meteorological database. The development of the hydrological operational multipurpose sub-programme (HOMs) has been one of the greatest achievements in this regard. However improvements should be made in the method of forecasting and promoting public awareness because of the enormous benefits. The network of instruments, satellite, and other meteorological flood prediction devices can be employed, coupled with the appropriate model to forecast in real time the onset and other features of the phenomena in question (Hendrick, 2007).

Development of some of these hydrological forecast systems in a number of countries has resulted in substantial saving of lives and some reduction in damages. Installation of similar systems would also reduce vulnerability of some areas and promote early evacuation of vulnerable areas. However, problems have been identified in relation to evacuation of people due to the resistance of population that has been subjected to flood. Smith (2006), observed that this was a significant factor in the lack of response to an evacuation order in New South Wales, Australia and noted that the effect of crying wolf as a factor that might make future evacuation more difficult if not impossible.

Oriola (2008) emphasized that in the many developing countries, especially in Africa, the weakness of state infrastructure, absence of appropriate legal and policy framework and sometimes inadequate resources particularly render them more vulnerable to the consequences of flooding and other natural disasters.

Occurrences of flood disaster

It is difficult to determine the extent of flood damages and to compare in satisfactory manner one flood with another due to the relative tendency to overestimate flood damages particularly at the time of the flood (Smith 2006).

In 1913, the damages from flood along the Mississippi and Ohio River were computed to be the excess of $ 162,000,000. The same magnitude of flood also occurred in Mississippi and Ohio in 2003. In 1955, Northern and Central California was subject to severe flood which resulted from continued heavy rains in the Mountainous areas. In March to May of 1965, the upper Mississippi and the Missouri river basin and the Red River of the North were flooded as a result of the melting of a heavy snow cover, whereas in this country, Nigeria, snow has never been experienced due to our tropical location and perpendicular position to the sun. In 2007, Pakistan, in the Middle East experienced an unusual flood which destroyed over 70 acres of land with properties worth over $2 million.

In Nigeria, the effect of flooding is mainly due to excess rainfall, urbanization and poor waste disposal. Flooding in Nigeria occurs in three main forms; River flooding, Urban flooding and Coastal flooding (Etuonovbe, 2011). Flooding of Ogunpa stream in Ibadan killed several people and completely grounded socio-economic activities. It also submerged 500 houses in different parts of the city. The flood occurred as a result of heavy rainfall and about 32 people died and 1000 injured from the incident

In Illorin, Kwara State, flood disasters has been recorded in 1973, 1976 and 1979. Recently, in August 2008, the residents of Makurdi were thrown out their houses and farm lands, left impoverished after two days of heavy down pour of rainfall which was described as disastrous (Akin, 2009).

Odjugo (2012) reports how a Lagos flood forced Lagosians to relocate as a result of heavy rainfall of 7th and 8th July 2011, not knowing that there was going to be a more devastating torrential rain that will result in more disastrous flood in Lagos metropolis in the following week. Flooding in Nigeria have at various time affected Nigeria cities, especially in the densely populated cities like Kano, Lagos, Port Harcourt, Aba, Ibadan, etc, destroying life and properties (NEST, 2011).

In early October of 2012, the River Benue, one of the two major rivers in Nigeria, which rises from North West Cameroun, was flooded due to excess rainfall which prompted to release more water from their dam. The result was increased unprecedented river overflow which flooded the whole states close to the river Benue and the states in the lower course of the river. At least 325 people have been confirmed dead and hundreds of thousands has been dislodged and a million farmlands have been submerged since the start of floods in July, raising concern about food security (NEMA, 2012.)

The popularized September – October 2012 flood destroyed more than 2 million houses in twenty cities and countless communities (NEMA, 2012.)

The flood occurrence caused panic in the whole countries and caused an astronomical rise in price of food crops, resulting to an estimated 2% rise in inflation rate in the country. This is in fact the worse flood experience the country has seen in a country as the impact is still felt all over most parts of the country. The government has spent over 100billion Naira (N100, 000,000,000) on relief materials for flood victims in the country. (NEMA, 2012).

In the face of the flood disaster that has currently submerged about one quarter of the country’s cities; many Nigerians are of the opinion that the deluge of flood that may not abate soon will have been mitigated. Poor and unavailable flood prediction and flood control systems and techniques are seen as the major cause that aggravated the flood disaster in a country.

Health implications of flooding

The he­alth implications of floods are far reaching and influenced by the close interplay between physical, social and other vulnerabilities, pre-existing health conditions, and flood characteristics including the speed of onset (flash floods more severe than slow onset), depth, and extent. The vulnerable groups iden­tified include the elderly, disabled, children, women, ethnic minorities, and those with low incomes. The speed of flood onset is the chief determining factor influencing the severity and frequen­cy of the health impacts and most health problems begin after the flood waters recede (Tunstell & Tunstall, 2007).

Notable health implications includes:

Mortality

The main reason for mortality is death by drowning/asphyxiation. A great burden is attributed to he­art attacks, hypothermia, trauma, and vehicle-related accidents and the speed of the flood water is a determinant of the number of immedi­ate flood-related deaths. Most drownings are associated with wading into fast mo­ving waters, and deaths by drowning in homes occur largely among the el­derly (Tunstell & Tunstall, 2007).

Morbidity

  1. Injury: Flood-related injuries are caused when individuals are evacuating from flood waters or attempting to save family and valuables. These injuries are usually minor in nature and inclu­de soft-tissue injuries such as con­tusions, lacerations, abrasions, cuts, bruises, sprains, strains, and punc­ture wounds.
  2. Communicable diseases and infections: As a result of flooding, communicable vec­tor-borne diseases such as malaria and dengue fever are common after floods. Leptospirosis, an emerging threat in most developing countries following flooding, is also of concern after flooding occurs in an area. Floods are known to be associated with increase in self-reported cases of acute gast­roenteritis and stomach upsets. General infections resulting from di­rect contact with flood waters include skin irritation and infection (dermati­tis), conjunctivitis, and ear, nose, and throat infections (Ujah, 2013). Respirato­ry symptoms reported include colds, coughs, flu, headaches, acute asth­ma, and pleurisy.
  3. Chronic diseases: Cardiac complaints, high blood pres­sure, cardiac arrest, kidney or other renal infections, erratic blood sugar levels, and heart attacks are usually reported af­ter flooding. Increases in chronic respiratory illnesses, especially wor­sening asthma, are also reported in most cases (Tunstell & Tunstall, 2007).
  4. Poisoning and animal bites: Some of the other health impacts re­ported include a few cases of snake bites as snakes tend to take refuge in households after flooding. There is also the potential threat of toxic fun­gal spread both in homes and in agri­cultural lands following floods (Tunstell & Tunstall, 2007).

Mental health implications

Most of the literature for mental he­alth implications from floods comes from high- and middle-income countries (Ahern and Kovats 2005). The men­tal health implications result mainly from the destruction during the event itself, loss of life and/or property, problems in the recovery period, geographic displacement, anxiety about event recurrence, and stress in dealing with builders and repair people in the af­termath. Several studies report common mental disorders such as anxiety, panic attacks, increased stress levels, mild/moderate/severe, depression, irritability, nightmares, sleeplessness, Post-Traumatic Stress Disorder (PTSD), anger, tantrums, mood swings, increased tensions in relationships (e.g., arguing), difficulty with concentration, suicidal thoughts, alcohol dependence, and psychoso­matic disorders (Etuonovbe, 2011).

Socio-economic implications of flooding

Flooding of areas used for socio-economic activities produces a variety of negative impacts. The magnitude of adverse impacts depends on the vulnerability of the activities and population and the frequency, intensity and extent of flooding. Some of these factors are as stated by Tunstell and Tunstall (2007) are shown below:

  1. Loss of lives and property: Immediate impacts of flooding include loss of human life, damage to property, destruction of crops, loss of livestock, non-functioning of infrastructure facilities and deterioration of health condition owing to waterborne diseases. Flash floods, with little or no warning time, cause more deaths than slow-rising riverine floods.
  2. Loss of livelihoods: As communication links and infrastructure such as power plants, roads and bridges are damaged and disrupted, economic activities come to a standstill, resulting in dislocation and the dysfunction of normal life for a period much beyond the duration of the flooding. Similarly, the direct effect on production assets, be it in agriculture or industry, can inhibit regularly activity and lead to loss of livelihoods. The spillover effects of the loss of livelihoods can be felt in business and commercial activities even in adjacent non-flooded areas.
  3. Decreased purchasing and production power: Damage to infrastructure also causes long-term impacts, such as disruptions to clean water and electricity, transport, communication, education and health care. Loss of livelihoods, reduction in purchasing power and loss of land value in the flood plains lead to increased vulnerabilities of communities living in the area. The additional cost of rehabilitation, relocation of people and removal of property from flood-affected areas can divert the capital required for maintaining production.
  4. Mass migration: Frequent flooding, resulting in loss of livelihoods, production and other prolonged economic impacts and types of suffering can trigger mass migration or population displacement. Migration to developed urban areas contributes to the overcrowding in the cities. These migrants swell the ranks of the urban poor and end up living in marginal lands in cities that are prone to floods or other risks. Selective out-migration of the workforce sometimes creates complex social problems.
  5. Psychosocial effects: The huge psycho-social effects on flood victims and their families can traumatize them for long periods of time. The loss of loved ones can generate deep impacts, especially on children. Displacement from one’s home, loss of property and livelihoods and disruption to business and social affairs can cause continuing stress. The stress of overcoming these losses can be overwhelming and produce lasting psychological impacts.
  6. Hindering economic growth and development: The high cost of relief and recovery may adversely impact investment in infrastructure and other development activities in the area and in certain cases may cripple the frail economy of the region. Recurrent flooding in a region may discourage long-term investments by the government and private sector alike. Lack of livelihoods, combined with migration of skilled labour and inflation may have a negative impact on a region’s economic growth. Loss of resources can lead to high costs of goods and services, delaying its development programmes.
  7. Political implications: Ineffective response to relief operations during major flood events may lead to public discontent or loss of trust in the authorities or the state and national governments. Lack of development in flood-prone areas may cause social inequity and even social unrest posing threat to peace and stability in the region.

Possible ways of controlling flood disaster

According to Burus (2010), the possible ways of controlling flood disaster are as follows:

  1. Construction of dams to create flood control reservoir, stream channelization and drainage scheme in build up areas.
  2. Run-off in low lying areas are to be properly controlled and channeled into well protected discharge basins such as swamp, stream outflows, etc.
  3. Long term measures should be planned by enacting strategic laws to regulate energy consumption (fossil fuels), in view of safeguarding the ozone layer and subsequent maintenance of a balance in global warming.
  4. Proper landscaping of land before building of houses.
  5. Planting trees on steep slopes to lower the rate at which water flows.
  6. Construction of pumping stations and water gates making sure that gullies work.
  7. Checking and cleaning of road gullies to ensure that they are not blocked or collapsed and where there is a large flowing towards a low spot, this area should be checked to ensure that adequate gullies are provided for effective channelling of water.

Management of floods

The following according to Burus (2010) are measures to manage flood:

  1. Mass education on the safety and education procedures
  2. Building of reservoirs to store excess water. This is used to hold water back. Dams are built to hold back flood.
  3. Proper and good environmental sanitation should be carried out through clearing of drains and waterways to reduce municipal flood.
  4. Buildings should be sited at least 5 ft away from drainage channels and totally avoiding dangerous flood- zones.
  5. Diverting of streams and rivers to less hazardous areas.
  6. Building high walls against overflowing rivers such as dykes and levees
  7. There should be proper management of soil and vegetation resources through afforestation and reforestation to reduce the rate of run-offs.

Conclusion and recommendations

The effects of flood hazards on man and its environment as well as socio-economic activities are enormous. Based on this, the following recommendations are made:

  1. There should be serious planning of the environment as well as need for drainage channels in order to curb the problems of annual and persistent flooding in the area.
  2. Well informed individuals should assist the Local, State and the Federal Government in passing information to the public on the implication of indiscriminate falling of trees, blocking of drains with weeds, collapsing of existing drainage systems and other activities which are precursors to inundation in the area;
  3. The local and state government in collaboration with the people of the community should embark on the construction of drainages which should be well planned to channel runoff water to nearby rivers/streams.
  4. Areas with depression should be sand filled to prevent convergence of runoffs especially at street/road junctions.
  5. Planners should specify habitable and non-habitable area so as to avoid flood hazard from affecting the lives and properties of the people.

References

ActionAid International (2006). Climate change, urban flooding and the rights of the urban poor in Africa, Key findings from six African cities, London: Books for Change

Akin, A. E. (2009). An Assessment of Flood Hazard in Nigeria: The Case of Mile 12, Lagos. Mediterranean Journal of Social Sciences. 3(2): 367 – 377.

Burrus, N. I. (2010). Urbanization, Climate Change and Flood Risk: Addressing the Potentials of Flood Risk Management in Nigeria Urban Environment. Conference Proceedings on Climate Change and the Nigerian Environment, held at the University of Nigeria, Nsukka. 29th June – 2nd July pp. 501 – 515.

Efe, S. I. (2010). Environment and Sustainable Development: The Case of Climate Change and Flood Hazards in the Niger Delta Region of Nigeria. A Paper Presented at The International Conference on Natural Resource, Security and Development in the Niger Delta Held on March 8-11, 2010 at Niger Delta Wetlands Center Yenagoa, Bayelsa State, Nigeria, p.13-15

Etuonovbe, A. K. (2011). Devastating Effect of Flooding in Nigeria. FIG Working Week, 18-22.

Gabler, R. (2010). Consideration for Improving Geographic Information System Research in Public Health, URISA 12 (2): 41 – 63.

Hendrick, K. (2007). A Framework for Evaluation of Flood Management Strategies. Journal of Environmental Management, 86(3): 465 – 480.

Horton, G. A. (2006). Technical Water, Water Quality, Environmental, And Water-Related Terms; Nevada: National Geographic Special Edition.

Hoyt, M. (2009). Risk Mapping of Flood Hazards in New Members States. EU Joint Research Centre, IPSC, NEDIES, EUR, 22902.

National Emergency Management Agency [NEMA] (2012). Evaluation of Flood Hazards Prepared by Environmental Impact Assessment Department. November 2012.

National Environmental Survey/Action Team [NEST] (2011). Flood hazard Assessment, Management and Mitigation Measures. Ibadan: A NEST.

National Technical Committee on Water (2008). Situation of Coastal Resources of Thailand, Office of Environmental Policy and Planning, Ministry of Science, Technology and Environment.

Odjugo, P.A.O. (2012). Valuing the Cost of Environmental Degradation in the Face of Changing Climate: Emphasis on Flood and Erosion in Benin City.  African Journal of Environmental Science and Technology 6 (1): 17 – 27.

Oriola, E. O. (2008). Strategies for combating urban flooding in a developing Nation. A case study from Ondo. The Environmentalist 14 (157): 62-100.

Resonzweig, K. A. (2009). Impact of Urban Growth of Flood Hazards in Makkah City. International Journal of Water Resources and Environmental Engineering. 4 (2): 23-34.

Smith, K. (2006). Floods: Physical processes and human impacts. London: John Wiley.

Tunstell, S. & Tunstall, S. (2007). The Health Effects of Flooding: Social Research Results from England and Wales. Journal of Water Health 4 (3): 356 – 380.

Leave a Reply

Your email address will not be published. Required fields are marked *