Example

UDC 631

Flood Vulnerability Modelling Factors of Nafada Town, Gombe State, Nigeria Using Remote Sensing and GIS Techniques

M.I. Muhammad ^{a , *} , U. Wali ^a , M.A. Modibbo ^a

^a Department of Surveying and Geoinformatics, Abubakar Tafawa Balewa University, Bauchi, Nigeria

* Corresponding author

E-mail addresses: (M.I. Muhammad)

Abstract

This study employs the integrated approach of Remote Sensing and Geographic Information Systems (GIS) techniques in flood management with the goal of deriving flood vulnerability modelling factors. Flood vulnerability studies have become more efficient in recent years because of the availability of advanced computational facilities and use of GIS. Almost every year, Nafada Town has been experiencing repeated flooding during the rainy season (July to September). As a consequence, properties are lost or destroyed and sometimes lives are lost. The aim of this research is to develop factors that could be used in flood vulnerability modelling of terrain features that favored the incidence of the floods as part of the solution to the problem. The objectives were to process Shuttle Radar Topographic Mission (SRTM) Scene 186/052 with a resolution of 90m·90m which covered the study area, downloaded from United State Geological Surveys (USGS) and the factors were obtained. These fetors were fill sink (elevation), terrain wetness index, proximity to river and overland flow length using the Integrated Land and water information system (ILWIS 3.3) Software, the factors were then classified using Natural breaks extension of ArcGIS 9.3 software. Hence, GIS techniques were proved to be useful in deriving the flood vulnerability modelling factors in a time and cost effective manner. It is recommended that GIS methods should be incorporated in planning and management of floods in the study area and further study should be conducted to combine these factors to develop a flood vulnerability model of the area.

Keywords: Flood, Vulnerability, GIS, Remote Sensing, Mission, Nafada Town, Modelling, Proximity, Overland, Terrain wetness Index.

1. Introduction

In simple terms, flood is defined as temporary covering of land by water as a result of surface water escaping from their natural confines or as a result of heavy precipitation (Opolot, 2013). Perhaps, in contemporary times, it is the most consistent serious natural disaster affecting most countries of the world. For instance, Asian countries have been at the frontline of the incidence and severity of flooding in the world. It is estimated that the countries experienced 1/3^rd of the 1562 floods that occurred in the world between 1994 and 2004 (Uddin et al., 2013; Bhatt et al., 2014). In Europe, flooding was reported in countries like Italy, Russia, Romania etc. (Ebi et al., 2003). It is even forecasted that the incidence of floods in Europe will double by 2050 while annual economic losses resulting from them will increase five folds (Conner, 2014). Thirty-two major floods occurred in the United States in the 20^th Century (Perry, 2000).

2. Study area

The location of Nafada town is at latitude 110928mN and longitude 113289mE. It is the administrative headquarters of Nafada Local Government Gombe State, north eastern Nigeria (Fig. 1). It has an average altitude of 306 m and a largely agrarian population of 22,920 according to the 2006 population census. The town has distinct wet (rainy) and dry seasons whose incidence is governed by the movement of the inter-tropical convergence zone, a zone where warm and moist air from the Atlantic Ocean converges with hot, dry, and often dust-laden air from the Sahara Desert known locally as the harmattan. The rainy season lasts for three months (July-September). The average rainfall varies from 760 mm to 1000 mm annually, with the highest rainfall recorded during the months of July and August. Temperatures are high throughout the year, averaging from 25 to 28 °C (77 to 82 °F).

3. Materials and methods

The Shuttle Radar Topographical Mission (SRTM) Digital Elevation Model (DEM), Scene 186/052 with a resolution of 90 m·90 m which covered the study area was obtained from (USGS, 2008). The ILWIS 3.3 was used for data processing. The flow chart in Fig. 2 describe how the DEM was processed to achieve the purpose of the study.

The SRTM DEM was imported into the ILWIS 3.3 environment and was process and the flood vulnerability criteria (fill sink/elevation, terrain wetness index, proximity, overland flow length) were obtained.

Classification is based on natural breaks using ArcGIS 9.3, classes are based on natural groupings inherent in the data. ArcMap identifies break points by picking the class breaks that best group similar values and maximize the differences between classes. The features are divided into classes whose boundaries are set where there are relatively big jumps in the data values. It is typical to use this type of thematic classification on continuous phenomena, such as slope, distance, or suitability, where you want to classify the range into a small number of classes and assign colors to those classes.

4. Results and discussion

The results obtained from the data processing described above are presented below.

Elevation

The graphical representation of the elevation values of the study area is shown in figures 3A and 3B. Fig. 3A show that the average geodetic height of the study area ranges from 246 m (lowest) to 499 m (highest elevation). Fig. 3B show that elevation is lowest (depicted in green) around the River and increases outwards to the height of about 499 m above sea level. This suggests a difference of 53 m between the lowest and highest elevations. This difference is large enough to ensure that in line with the law of gravity, the low lying river and its immediate vicinity is the destination of runoff from surrounding higher elevations.

5. Conclusion and recommendations

Nafada town and its environment has been experiencing flooding over the years, this according to the research has been attributed to many factors amongst which are excess stage discharge, vulnerability, nature and rate of the Terrain Wetness Index, Proximity to the river and Geodetic Height of the area. High Terrain Wetness Index is recorded in areas around river Nafada, significant percentage of the area is low-lying, larger percentages of the people lives very close to the river, hence with close proximity to the river Nafada, the vulnerability and susceptibility of the people to flooding is very high. Hence, the application of this method (RS and GIS) in Nafada to developed flood vulnerability factors like Terrain Wetness Index, DEM, Proximity to the river and overland flow length, it is in no doubt a holistic approach in flood management in the Nafada town and its surroundings. This study was conducted under major constraint of limited data availability. Therefore, the following recommendations are made for the further studies in the future.

References

Opolot, 2013 – Opolo E. (2013). Application of remote sensing and GIS for flood hazards management review, Research Journal of Applied Science, Engineerig and Technology, 6(10), 1884-1984.

Uddin et al., 2013 – Uddin K., Gurung D. R., Giraraj A. and Shrestha B. (2013). Application of remote sensing and GIS for flood hazards management a case study of Sindha province Pakistan. American Journal of GIS, 2(1), 1-5.

Bhatt et al., 2014 – Bhatt G. D, Sinha K, Deka P. K. and Kumar, A. (2014). Flood hazards and risk assessment in Chamoli district Uttra Khand using satellite remote sensing and GIS. International Journal Of Innovative Research In Science, Engineering And Technology, 15348-15356.

Ebi et al., 2003 – Ebi K. L., Kobat R. S., Menne B., Edward, Hajjat, S. and Heinne, S. (2003). The human Health consequencies of flooding in Europe: a review. Journal Of Applied Environmental Science And Public Helth, 1, 13-21.

Conner, 2014 – Connor S. (15 May, 2014). Indipendent Newspaper of UK retrived at http://www.climatecentral.org

Perry, 2000 – Perry C. A. (2000). Significant floods in the United States during the 20^th Century – USGS measures a Century of floods. USGS Fact Sheet, 024-00. Retrieved from http://www.ks.water.usgs.gov

Emmanuel, 2013 – Emmanuel G. (13 June, 2013). Reliefweb. Retrieved from http://www.reliefweb.int

Whitworth et al., 2015 – Whitworth, M., Brian, B. and Nkwunonwu, U. C. (2015). Flooding and Flood Risk Reduction in Nigeria: Cardinal Gaps. Journal of Geography and Natural Disasters, 5, 136-145.

NEMA, 2012 – National Emagency Management Agency (2012). Annual Report on floods. Retived at http://www.nema.gov.ng

NEMA, 2013 – National Emagency Management Agency (2013). Annual Report on floods. Retived at http://www.nema.gov.ng

NEMA, 2014 – National Emagency Management Agency (2014). Annual Report on floods. Retived at http://www.nema.gov.ng

NEMA, 2015 – National Emagency Management Agency (2015). Annual Report on floods. Retived at http://www.nema.gov.ng

Nafada LGA, 2013 – Nafada Local Government Area. (2013). Annual reports on projects executed by the council.

Nnodim, 2016 – Nnodim O. (26 July, 2016). There will be flooding in 14 States, says NIHSA. Retrived at http://www.emdat.de

Davies, 2016 – Davies R. (14 June, 2016) Nigeria – Thousands left homelessafter floods in Ebonyi. Floodlist.

Eleazu, 2016 – Eleazu, U. (21 June, 2016) Flood kills three, destroys 150 houses in Nassarawa. Bespoke pan African online newspaper. Retrived at http://www.reportsafrique.com

Doocy et al., 2013 – Doocy S., Daniel, A., Murray S. and Kirsta T. D.. (2013). The humman impacts on floods a historical review of event 1980-2009 and systematic literature review ISSN 2157-3999. Retrived at http://www.currentplos.org