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Flood vulnerability assessment of donstream area in Mono basin in Yoto district, south-eastern Togo

par Abravi Essenam KISSI
University of Lome - Master 2014

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1.1. Problem Statement

Many countries worldwide, whether in Europe, America, Asia, Oceania, Australia or in Africa, are experiencing heavy rains, river overflows, hurricanes, typhoons, tsunamis causing unexpected floods which decimate entirely or partly some localities in all over the world. Floods are among the most recurring and devastating natural hazards, impacting human lives and causing severe economic damage throughout the world (Sadiq et al, 2011, p 85). Floods can be defined as hydrological events characterised by a rapid rise of water flow in the river. They are characterised by long, short and no warning, depending on the type of floods, speed or onset which may be gradual or sudden (Carter 1991, p1). Various elements either climatic or non-climatic influence flood processes resulting in different types of flood. Six types of floods are distinguished: coastal, flash, river, flood due to drainage problems, tsunamis, and tidal wave/bore floods (Jonkman, 2005).

Flood disasters are occurring as a consequence of either natural factors, such as climate change and climate variability or anthropogenic factors, such as socio-economic and land-use developments (Balica, 2009, p 2571). The frequency of those disasters has been increasing over the years, resulting in loss of life, damage to property and destruction of the environment.

Over the last 50 years, there has been a growing body of evidence pointing to the effect of human behaviour on the global natural environment and on the possibility that certain types of natural disasters such as floods may be increasing as a direct consequence of human activity (Guha-Sapir et al, 2004, p 15). Equally, the effects associated with global warming such as sea level rise, more intensive precipitation levels and higher river discharges may be consequences of this as well. Those effects may increase the frequency and the extent of flood hazards on a worldwide scale and make the number of people at risk in developing countries more vulnerable to flood disasters due to high poverty level.

In Africa, floods of different kinds are one of the most common type of disastrous events, and they account for the biggest losses inflicted by natural disasters. The UN Office for the Coordination of Humanitarian Affairs (OCHA) recently stated that, compared with previous years, 2010 has seen the largest number of people affected and dying from flooding. This is consistent with the dramatic rise in flood events that have battered the world, with West Africa being a case in point.

It is understood that flood risks will not subside in the future, and with the onset of climate change, flood intensity and frequency will threaten many regions of the world (Sadiq, 2011, p 85). The Fourth Assessment Report (AR4) by the Intergovernmental Panel on Climate Change (IPCC, 2007) projects that warming in Africa in the 21st century is likely to be greater than the average global warming and does find that extremely wet seasons, high intensity rainfall events, and associated flooding in West Africa are expected to increase by 20% over the next decades. However, it is noted that responses of local communities to the impact of extreme climatic events in many cases in West Africa have mostly been reactive instead of proactive.

Between 1925 and 1992, Togo has recorded 60 urban and rural floods that caused damages and casualties (MERF, 2013, p 13). Flood disasters are not then a recent phenomenon in the country but have become a frequently recurring problem that occur mainly between July and October which inflicts significant environmental, social, and economic damages and affects population safety. According to "EM-DAT" (Emergency Events Database) of the Centre for Research on the Epidemiology (CRED), a number of flood disasters have been recorded during the last 20 years, with particularly severe events occurring in 2007, 2008 and most recently in 2010 "figure 2". According to MERF (2010), the 2010 flood, in Togo has impacted both urban and rural areas throughout the entire country, affecting 82,767 people; 21 persons were reported to have lost their lives, 85 to have been injured, 12,382 houses have been impacted and 7744,24 hectares of land to have been destroyed. Damage and losses were amounted to an estimated 1.1 percent of GDP, amounting to US$38 million.

Figure 1: Number of people affected by flood during the period of (1994-2010)

Source: EM-DAT: The OFDA/CRED International Disaster Database

The study area is made up of eight villages (Mawussou, Djrekpon, Batoe, Tofacope, Atikpatafo, Logokpo, Tchakponou-kondji, Kpodji) from three counties Sedome, Esse-Godjin and Tokpli located along the river in a severely flood prone area. The population has experienced occurrence of floods. Flood events were frequent during the last decade, causing loss of lives, extensive damages to property, including houses, destruction of transport infrastructures, agricultural land, breakdown in education system and food production. In sum flood affects human security in these communities. The number of reported flood disasters during the last 20 years in the Yoto area, occurred mainly in 1995, 1999, 2007, 2008 and 2010, with the 2010 flood being the most severe (UN, 2010) and recently in October 2014. During the 2010 flood, six counties, 35 villages, including the study villages, were impacted; 2081 people were affected and 1496 hectares of crops were destroyed in the area. Supplied by a set of sub-branches, the Mono River with 21,300 km² often undergoes during torrential rains period, the rising of water level followed by high flows causing the overflowing of the river which inundates the selected villages and makes the population more vulnerable to flood disasters. To this are added environmental factors such as fragmentation of the river banks due to erosion effect digging and widening the river channel, the anthropogenic pressure like the construction of Nangbeto dam at the upstream of the Mono basin, deforestation, the demographic explosion and the socio-economic constraints that exacerbate the vulnerability of the population located at the downstream part of the basin (AGO et al., 2005, p 1).

The country's vulnerability is expected to increase as a result of climate change. It follows that both the frequency and the severity of flood hazards have the potential to increase (MERF, 2009). Regardless of the current and the future trend of flood hazards combined with socio-economic constraints of the area, about 74.8% of people are below the poverty line (IMF, 2010, p 17), the occupancy or use of flood-prone areas may involve a degree of vulnerability.

For communities to be protected against damage due to floods, it exists four main type of flood measures that have to be taken into account: the non-structural measures, the structural measures, land planning measures and conducting flood vulnerability and risks assessments, the latter being the first step in disaster risk reduction process. Therefore, to enable decision makers to implement appropriate flood policies in the right place, there is a need to conduct flood vulnerability assessment with a vulnerability score for a systematic understanding of an area; its characteristics related to flood disasters and easily interpret and compare vulnerability of different communities. Thus, the focus of this study is to conduct flood vulnerability assessment of the downstream area in the Mono River basin in the Yoto district through indicator-based vulnerability assessment as proactive response to floods.

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