GEOINFORMATION ASSESSMENT OF DAM FAILURE VULNERABILITY IN *Salamatu, L. A1, Hauwa, .M.A1, Mahmud,U1, Oluwafemi, O.A1, Adepoju, K.2, 1Centre for Geodesy and Geodynamic (CGG), Toro, , Nigeria. 2Obafemi Awolowo University, Ile- . E-mail:[email protected] Abstract:

Dam has become a widely distributed and devastating disaster that has caused significant damages both economically and socially in Nigeria. Dam failure has caused more harm than good, Dam failure are caused by flood event, geological/foundation weakness (earthquake), storms and other human activity. Flooding originated from different levels of human environmental system which can lead to Dam failure. Flood event in Nigeria have pushed rivers over their banks and submerged hundreds of kilometers of urban and rural lands. Flash flood are common features in Nigeria during the raining season. This study therefore aims at creating a database and mapping of vulnerable area to dam failure using geospatial techniques. SRTM DEM was developed with ARCGIS 9.3 to identify vulnerable areas in both Towns/Villages as well as LGAs, the DEM was reclassified to highly vulnerable, moderately vulnerable and low vulnerable, using interval of less than 50m, 100m, 200m elevation from Dam 500m Buffer and River 300m Buffer. The study shows that 17 LGAs in Nigeria are vulnerable to dam failure after the buffering analysis was carried out and a total of 33 states are vulnerable to event of Dam failure. KEYWORD: Flooding, Vulnerability, Dam failure, Disaster, Nigeria

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INTRODUCTION

The earth is a combination of different natural systems which occurred uninterrupted before the existence of human beings. Geophysical events such as earthquakes, volcanic eruptions, landslides, spread and retreat of water along the river plains took place as a part of natural systems. Pandey, (2009)Natural hazards are the events or natural phenomenon that threatens or act disastrously in different space and time. When the natural hazards affects the environment and leads to financial environmental or human losses then it is called natural disasters. Natural disasters can be associated with many phenomenon such as the movement of the earth surface

(earthquakes, mass movement), water (floods, tsunamis, storms) and fire (wild fire) Gillespie et al, (2007).Water resources in Africa seems abundant, Average annual flow is over 4000 billion m3, and includes the world’s longest river (the Nile) and it’s second largest in terms of basin and flow is the Congo. The wet equatorial zone produces 95 per cent of Africa total flow, while the semi-arid and arid zones produces only 5 per cent .Floods are of many types which includes flash flooding, flooding due to rising ground water Gruntfest and Handmer,( 2001), coastal flooding, and flooding due to the opening or breaking of dams or reservoir Forkuo,( 2011). Flash flood can occur within minutes or hours of excessive rainfall or a dam or levee failure or sudden release

Jeyaseelan (1999). Dams which are constructed for a number of purposes such as provision of drinking water, recreation, irrigation and hydropower. If any outbreaks causes loss of life and affects agricultural products seker et al (2001). Dams and reservoirs provide important water storage for human and agricultural consumption and use, flood control, hydroelectric production, navigation, and recreation. However, along with the benefits, dam can also pose serious risk for the downstream river basin, agricultural land, historical sites, wildlife habitat and communities in the event of a catastrophic dam failure (breach). Whether caused by natural forces or terrorist attack, a catastrophic event like a dam failure is of great concern to local government officials in

2 terms of community preparedness and response. Dam failures happen. There are many reasons why a dam may breach: geological/foundation weakness (example: earthquakes), extreme storms which cause dam to overtop, structural problems, old age, terrorism, etc.

Aim: The aim of this study is to assess the human vulnerability to Dam Failure hazard in Nigeria with a view of providing policy makers a framework for monitoring and responding to environmental hazard.

Objectives

The objective of the study are to:

The specific objectives includes:  To create a Geographic Information System (GIS) Database for Dam location in Nigeria;  To examine the vulnerability level of each community where the Dams are located;  To create public awareness and increased public participation in land use planning. Study Area

Nigeria, officially the Federal Republic of Nigeria, is a federal constitutional comprising 36 states and its Federal Capital Territory, Abuja. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon inthe east, and Niger in the north. Its coast in the south lies on the Gulf of Guinea in the Atlantic Ocean. Its cover a total

Area of 923,768km2 /356, 667, sq. mi. Nigeria has a lot of Rivers and Dams which serve as means of hydropower, drinkable water, conservation area, recreational area, Transportation,

Tourism and irrigation. Some of which includes the , shiroro dam, Gubi dam, Eleyele dam, Doma dam, Bosso Dam etc.

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Figure 1.1The Study Area

Source: Salamatu (2014)

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MATERIALS AND METHODS

Data Types and sources

In other to achieve the objective of the study both primary and secondary data which contains both spatial and non-spatial (attribute) were used. The data used includes:

1. TheAdminstrative Map of Nigeria showing the states

2. Local government map showing villages and Towns

3. Digital Elevation Model (DEM) of Nigeria at 30m resolution sourced from

www.srtdem.org`

4. Google earth pro

Data Processing and Preparation

Google Earth

Using Google earth, locating the Map of Nigeria the Dams were digitized with the required coordinates, and each of the Dams digitized was exported into the ArcGIS 9.3 version environment, the digitized Dams was formally in the format of KMZ. In the ArcGIS 9.3 version the Dams digitized was converted into shape-files after being exported. The digitized Dams was overlaid on the DEM of Nigeria as well as the administrative boundary of Nigeria.

AdministrativeMap of Nigeria

Using ArcGIS 9.3 version software the maps was imported using the Geo-tiff format from the

C:\ drive, The map was Geo-reference and digitized, together with the 36 states and the federal capital territory Abuja as well as the drainage, The shape-files of the villages/towns and the

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Local government area was also imported into the ArcGIS 9.3 version environment and the layer added to the Map of Nigeria.

Methodology to Achieve Each Objective

Objectives 1: To map out the Drainage and Dam

Using ArcGIS 9.3 version the drainage was digitized on the map of Nigeria and the dams where digitized from Google earth which was converted to shape-file and then overlaid on the map of

Nigeria. The criterion used for mapping out was based on proximity analysis in which the Buffer tool was used to Buffer River at 300m and Dams at 500m radius

Objectives 2: To delineate and map out the vulnerability of villages and towns to Dam failure

The Dam vulnerability area are areas that are likely to be flooded when the river overflow its banks, which leads to dam break or dam failure. The delineation and mapping of the vulnerable villages and towns is crucial for vulnerability assessments. The vulnerable areas was extracted from the DEM which was generated from the digitized contours of the shuttle Radar Topography

Mission (SRTM). The dams where digitized from Google Earth and exported to ArcGIS 9.3 version and overlaid on the Map of Nigeria as well as the DEM. Triangular irregular Networks

(TIN) was also generated from the contours extracted from the SRTM. The criterion used for delineating the flood vulnerable area was based on proximity analysis in which the Buffer tool was used for the delineation and also height (elevation) and this was achieved using the DEM which was therefore categorized into very highly vulnerable, highly vulnerable, moderately vulnerable, low vulnerable and very low vulnerable to dam break/ flood, the delineated criterion includes

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1. Villages/Towns within 500m buffer of a dam

2. Villages/Towns within elevation less than 50m within 500m buffer of a dam

3. Towns within river dam buffer zones

Objectives 3: To delineate and map out the vulnerability of the Local government areas

(LGAS)

Using ArcGIS 9.3 version, the map of Nigeria was digitized and the shape-file of the LGAS was overlaid, the dam 500m buffer was overlaid as well as the river 300m buffer which shows LGAS that falls within the buffer zones of the dam. Buffers are usually used to delineate protected zones around features or to show areas of influence, buffer can be used to select features in another feature class or they can be combined with other features using an overlay tool to find parts of features that fall in the buffer areas. The river and the dam was buffered. The output result shows the LGAS that are within river and dam buffer.

RESULTS & DISCUSSION

Results

The results of the study includes the production of thematic map of Dams location and Drainage,

Towns and Villages vulnerable to Dam failure as well as LGAs and states in which the Towns and Villages are located. The results located also includes proximity analysis (Buffering) to determine settlements that are vulnerable Dam failure and identifying locations that are prone to

Dam failure within the study area.

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Drainage and Dam (Objective 1 Result)

Figure 3.1: Dams location and Drainage patterns Source: Salamatu (2014)

Figure 3.2: Map of Nigeria showing settlements within 500m radius of Dam location

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Source: Salamatu(2014)

Figure 3.3: Digital elevation model overlaid on the Dam location Source: Salamatu (2014)

Figure 3.4: Digital elevation model showing states within elevation of Dam and River Source: Salamatu(2014)

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Figure 3.5 : Showing the Local Government within the Buffer zones of both Dam and River Source: Salamatu (2014)

Table 2: Showing settlement within 500m < 50m height within the Dam locations

S/N States Towns/ Villages 1 Kwara Wasa, Bajibo, Ilukaji, Gungikorku, Gana, Fort-Goldie, Sungogi, Mushim, River moshi, Leaba, , Djebba, Dada, River Awun. 2 Kebbi Gulbinwaiya, TunganWakili, TunganMakeri, TunganGimba, Bamaraba, Sadawaika River pada, Matiakuka, Kainji lake, Gwaiya, Bussa. 3 Niger Yunu, Yunmu, Yankade, Buko, Bukah, AwuruEmigi, Tungan- Dangaje, TunganBarace, Yakedi, Tungankikwashi, TunganTeku, Falla, Faku, River Eku, Chegu, Karandadi, River Kontagora, Komi, New Kurwasa, Mahita, Kokodi, Karo, otiRiviere, Oly, Oli, River Oli, Niger dam, Shagaunmu, Sabo leaba, New tunganDangage, New Shagunmu.

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Table 3: Showing settlements within 500m< 100m Height of Dam locations

S/N State Town/Villages 1 Kogi Yasisule, Wodata, Wara, Shikaku, Onyebu, Okume, Aseni, Oti, Koto- karfe, River ofu, Gegu-beki, Koji, Egabada, Bagana, Agobada, Afa, Adana, Bugana, Ogurugu, Bnou, 2 Plateau Yamini, Zebir, Gindiri, Gwaji, Daffo-East, Gengere 3 Abuja Dnako, Abaji 4 Kwara Tachi, Omugo, Omode, Moshi, Lere, Ajasse, Ajasse-Ipo, Gana, Ilu-kaje 5 Gombe Delul, Malari, Lomi, Kuraje 6 Niger AwuruEmigi, Berikago, Faku, Falla, Gategi, GidanBahago, GulbinBoka, Kuraa, Kontagora, Kuka, Lawo, Ndimana, Ndimawa, Oli,oly, Rawo, Sumaila, RafinYaki 7 Zuwo, Zuwa, Wangara, UnguwarBado, Sani, RugarDuka, Madobi, Lerbi, Koginsani, KarfiRuga, Karfi, Gora, Fayamfayam, FarinDutse, Dalili, Alore,

Discussions

The study reveals that over 50 dams as well as rivers has been identified with respect to their geographical Coordinates, Dams such asKainji dam, Asejiri dam, Dadin- kowa dam, Gubi dam,

Jibiya dam, Eleyele dam, Jebba dam, , Oyan dam, , , Ajiwa dam,

Ikere gorge, Karfin-zaki dam, Shen dam, Guzuguzu dam, Iwo Ayuba dam amongst others. The capacity of the Dams varies from 10,800000m3 to 46,000m3 and flood flow varies from

877.3m3/s to 3.257m3/s. The study reveals thatTigaDam in has the highest capacity while Eruwa dam in has the least capacity. Figure 3.1 shows the Buffered zones of both the Dams and Rivers. The Dams were buffered with 500m buffered while the River were

300m Buffered, the study shows that 33 states where these dams were located are refered to as

11 vulnerable areas as shown by the proximity analysis i.eBufferring and this agrees with the report of Humanitarian Dashboard on 2012 flood that occurred in Nigeria in which 35 out of the 37 states were affected, life’s and properties was affected as well, over 7.7 million people and displaced 2 million individuals. The result of the study also agrees with OJigi et al, (2013) identified flood event of 2012 in central part of Nigeria which includes Kogi, Niger, Kwara,

Nassarawa and Benue state based on physical, social, economic and environmental factors.

Nabegu,(2014) identified household vulnerable to flood in Kano state by zoning the areas into three zones which consist of Fagge as zone 1, Bichi zone 2, and Tundunwada Zone 3 and this communities are also in line with the result of this study. Ikusemoran et al,(2013) identified flood risk and vulnerability of communities in the Benue floodplains, Adamawa, which was caused from the lagdo dam in Cameroon, over 120 communities were identified as vulnerable communities includes Bali, Faran, Kukawa, Jarumi, Wuro Ali, WuroBabawa, jimeta, Koh,

Kagalong, etc, this communities are also inclusive in the result of this study. Figure 3.3 and 3.4

Shows DEM and settlements vulnerable to dam failure hazard. The hazard vulnerability was categorized as highly, moderately and less vulnerable, using ground elevation of 50m height and

Dam location buffered at 500m radius. The areas on terrain elevations 50 – 100 were categorized as highly vulnerable, while 100 – 200 moderately vulnerable, 200 ─ 500 vulnerable, 500 –1000 low vulnerable, and 1000 ─ 2419 very low vulnerable respectively. The DEM analysis shows that Kwara, Plateau, Gombe, Abuja, and Kogi are highly vulnerable, Niger, Kano, Kebbi,

Plateau, Bauchi, Jigawa, Sokoto, Kaduna, and Adamawa are moderately vulnerable while Oyo,

Osun, Ogun and Ekiti are low vulnerable (fig 3.4). These result agrees with the Humanitarian dashboard report on 2012 flood and other research carried out, the report on 2012 flood and research carried out shows that Kogi, Plateau, Taraba, Benue, Edo, Kwara, Delta and Bayelsa are

12 the most affected state and the potential implication of the impact of the flood are health hazard, food shortage and infrastructure failures. Based on the analysis of this study, shows similar result except for Bayelsa, Edo and Delta state which was not shown as affected state and this is because the analysis carried out was based on Dam 500m Buffer and 300m river buffer, Table 2 shows detailed results of settlements within 500m<50m height. The buffering analysis shows that 67 settlements were vulnerable total of 67 Towns/villages. Table 2 shows a detailed result of

Town/Villages within 500m<100m Height of the Dam Buffer which is categorize as moderately vulnerable, a total of 76 Towns/Villages were affected and 500m<200m height of the Dam

Buffer is termed less vulnerable and has a total of 79 Towns/Villages affected respectively. The elevation of the surrounding areas relative to the river contributed more in determining their vulnerability levels as well as the distance from the river. For example an area that lies right beside the river may not be liable to flood if it is at a great height, however an area that lies further away may flood if the intervening land is flat or a gentle slope or if the area lies in depression. Figure 6 shows the vulnerability map of Towns/villages within Dam 500m Buffer, from the result it shows that 181 Towns/villages were vulnerable. Figure 3.2 shows the map of

Towns/villages within Dam and River Buffer, A total of 517 Towns/Villages were vulnerable based on the analysis most of this Towns/Villages were also affected during the 2012 flood event. Also in delineating flood vulnerability and Mapping of LGAs, Figure 3.5 shows vulnerability map of LGAs within Dam 500m Buffer and River 300m Buffer, From the Map on

Figure 3.5 a total of 206 LGAs are vulnerable based on the Buffering analysis carried out Table 5 shows the result of LGAs within the Dam Buffer, A total of 71 LGAs were within the Buffer zones from 19 states which includes Adamawa, Bauchi, FCT, Gombe, Jigawa, Kaduna, Kano,

Zamfara, Kebbi, Kogi, Kwara, Niger, Ondo, Osun, Oyo, Plateau and Yobe respectively. The

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LGAs includes funkayes, Kwami, Yamatu, Birnnwa, Guri, Kirikasa, Agwara, Magama, Iwo,

Odo-Otin, Barkin- ladin Jos-North, Jos- East, Chikun , Igabi Yola-North, Yola- South etc.

Conclusion

This study has provided information that would be helpful in floodplain, Dam failure monitoring, also identify settlements that are vulnerable to dam failure hazard. It also serves as a model for evaluating Towns/villages vulnerability to Dam failure as well as giving early warning sign in case of Dam failure occurrence.This study also clearly identifies states that are vulnerable to

Dam failure and 33 states were vulnerable, which when compared with the report of

Humanitarian dashboard on the flood event of 2012 which occur due to the lagdo dam failure in cameroon corresponds to the result obtain which affected over 3,870 communities. Also over

300 Towns /villages in those states were also vulnerable after the Buffering analysis was carried out and about 200 local government area in the states was also affected, based on the percentage carried out with the result obtain from analysis of Dam, shows that Kano and has the highest percentage and Adamawa, FCT and Kebbi states has the lowest percentage. The study also categorized the DEM based on very high vulnerable area to low vulnerable areas of

Towns/villages within 500m<50m height figure 7, Towns/Villages within 500m<100m,

Towns/Villages within 500m<200m height Dam buffer and table 2, 3 and 4 shows the result.

4.1 Recommendation

All communities that are found to be highly vulnerable to occurrence of dam failure which leads to flooding are recommended to be urgently relocated to higher grounds to prevent future occurrences.

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There should be a comprehensive mapping and inventory of all flood plains in Nigeria for proper planning, awareness and enlightenment of flood prone communities in the country.

Evacuationand disaster response protocols should be instituted with allocation for emergency shelters and distribution of relief materials in the event of Dam failure.

Dredging operation should be carried out to allow the river flow freely through its natural channel.

All the government, private and non-government organization that are involved in flood monitoring and management should imbibe the use of GIS for data generation and decision makings.

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Addis Ababa, Ethiopia. Forkuo, E., (2011), Flood hazard mapping using Aster Image data with GIS Volume 1, No. 4, 2011. Gillespie, Micheal, J., and David, F. (2007), Community disaster vulnerability theory, Research AndPractice Gruntfest, E., and Handmer, J., (2001), coping with flashflood TC 530 C67. 2001 North Atlantic treaty. Ikusemoran, M., Anthony, D., and Maryah, U.M. (2013), GIS Based Assessment of flood Risk and Vulnerability of communities in the Benue floodplains, Journal of Geography and Geology Vol. 5, No. 4, 2013. 15

Ikhuoria, I., Yesuf, G., Enaruvbe, G.O., and Ige-Olumide, O., (2012). Assessment of the impact of Flooding on farming communities in Nigeria: A case study of Lokoja, Kogi State Nigeria. Proceedings of the Geoinformation Society of Nigeria (GEOSON) & Nigeria Cartographic Association (NCA) Joint Annual Workshop/conference held Regional Centre for Training in Aerospace Surveys (RECTAS), Obafemi Awolowo University, Ile-ife, Nigeria, 19th -22nd November, 2012.pp.156-167 Jeyaseelan, A.T., (1999), “Droughts and floods assessment and monitoring using remote Sensing and GIS Application in Agricultural Meteorology, Pages 291-313.

Nabegu, A.B., (2014), Analysis of vulnerability to flood disaster in Kano state, Greener Journal of Physical Sciences Vol. 4(2), pp. 022-029, 2014.

Ojigi, M.L., Abdulkadir, F.I. and Aderoju, M.O., (2012), Geospatial Mapping and Analysis of the 2012 flood Disaster in Central parts of Nigeria. A paper presented at the Eight National GIS Symposium Damman. 15-17 April, 2013, Saudi-Arabia. Ojigi, M.L., (2010), Flood Hazard and Risk Mapping of Birnin-Kebbi and Environs, Using Geospatial Techniques. Journal of Geographic Information Science Vol. 1 no.1 (Maiden Edition), 2010. A Technical/ Scientific publication of Geoinformation Society of Nigeria (GEOSON). Pandey, S., (2010), Cloud computing technology and Geographical Information System from Computer and engineering view (ASGIS). 2010, ChongQing. Seker, D.Z. Kabdashi, S., and Rudvan, B., (2001), Risk Assessment of A Dam Break, Using GIS Technology, Istanbul, Turkey. Salamatu, (2014), Analysis of vulnerability of Dam failure in Nigeria using GIS technology Submitted to ARCSSTE-E, Award of Post graduate diploma in Remote Sensing And GIS, Ile-Ife, Nigeria. World Environmental Day (2014): Raise your voice, Not the Sea Level, proceeding of the Seventh Annual Conference of the Institute of Ecology and Environmental Studies, 24th -26th June, Vol. 7, Obafemi Awolowo University, Ile-Ife, Nigeria.

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