Ethiopian Journal of Environmental Studies & Management 10(2): 229 – 240, 2017. ISSN:1998-0507 doi: http://dx.doi.org/10.4314/ejesm.v10i2.9 Submitted: December 06, 2016 Accepted: March 13, 2017

MORPHOMETRIC AND LANDUSE ANALYSIS: IMPLICATIONS ON FLOOD HAZARDS IN ILESA AND METROPOLIS,

AKINWUMIJU, A.S. Department of Remote Sensing and GIS, Federal University of Technology, , Nigeria Email: [email protected]

Abstract This study assessed the morphometric, landuse and lithological attributes of five basins (Iwaraja, Ilesa, Olupona, Osogbo I and Osogbo II) with particular reference to flood hazards in Ilesa and Osogbo metropolis, Osun State Nigeria. Ilesa town is situated within Iwaraja and Ilesa basins while Osogbo metropolis spread across Olupona, Osogbo I and Osogbo II basins. Twenty-three morphometric parameters were computed from DEM- based vector data for the sub-basins using GIS techniques. Image analysis technique of unsupervised classification was adopted to generate landuse map for the sub-basins. Classification was based on six landuse classes that were identified on the satellite imagery and confirmed by field investigations. Statistical analyses of the classification results were undertaken. Also, lithology of the basin was analyzed. Morphometric characteristics of Osogbo I, Osogbo II and Olupona drainage basins have the tendency to trigger high impact floods while flood hazard is relatively low in Iwaraja and Ilesa basins. However, relief attributes suggest possible exposure to flash flood particularly along the banks of main channel of Ilesa basin. Landuse analysis indicates that more than 85 percent of Osogbo I, Osogbo II and Olupona basins are built up and consequently impervious, leading to low infiltration-runoff ratio. Less than 32 percent of Iwaraja and Ilesa basins are built up while more than 66 percent of the basins are covered by vegetation of varying degrees of thicknesses, leading to high infiltration-runoff ratio. Occurrences of heavily fissured quartz schist in Iwaraja basin also contribute to high infiltration potential in part of Ilesa town. Consequently, Osogbo metropolis is highly susceptible to flood hazards compared to Ilesa town where potential flood dangers are easy to manage.

Keywords : Morphometry, Landuse, Flood Hazards, Exposure, Urbanization

Introduction drastic fall of standard of living of For several decades flood has been a humans (Komolafe et al., 2015). The global annual occurrence that usually occurrence of flood has been linked to claims both lives and properties, leading many causes that could be natural or to sudden reverse in development and manmade. The natural causes include

229

Morphometric and Landuse Analysis: Implications on Flood Hazards ...... AKINWUMIJU, A.S. heavy rainstorm, prolong torrential when Ogunpa River flooded its rainfall, ocean storms and tidal waves plain within the metropolis, causing (Atedhor et al., 2011; Adedeji et al., severe damages to lives and properties 2012; Agbonkhese et al., 2014; Ijigah (Adedeji et al., 2012). Ever since, flood and Akinyemi, 2015). Anthropogenic has been a major disaster laden causes include sudden burst of major occurrence across Nigeria. Poignantly, trunk water pipes, dam and dyke failure flood occurrence has been on the increase and excessive ecological release from and of greater impacts in Nigeria’s overflowing dam (Atedhor et al., 2011; settlements since year 2000. This is not Olawuni et al., 2015). In some cases, the unconnected with climate change and occurrence of flood downstream of a variability, leading to shorter raining major river might not be connected to in season, increased raining days and higher situ rainfall; but the accumulation of intensity and duration of rainfall. The excessive discharges from tributaries at effect of climate change has equally been the upper course of such a given river. In aggravated by reduced vegetation cover this case, causes of flood are usually and vitality, buildup of natural flood extensive. plains, channel modification and Flood would remain an event if it obstruction of river courses. Recent does not inflict damages on lives and population explosion and its consequent properties of humans as well as economic urbanization have resulted to increased activities and natural resources. But when exposure of lives and properties to flood humans and their economic activities, hazards in Nigeria. Poignantly, exposure properties and natural resources are has been on the increase due to lack of exposed to flood, the end result is proper urban planning and policy, leading disaster, which (many at times) is capable to indiscriminate and uncontrolled of destroying the livelihood of people. development in virtually all Nigerian Thus, while humans (in some cases) will settlements. As it is in the developed have to adapt and cope with the menace countries, there is the need to shift from of flood disaster, its occurrence could flood disaster management to flood (sometimes) be averted. This could be prevention and mitigation. In this case, achieved through landuse planning and studies on flood events should cut across urban renewal, reduced interference with an entire drainage basin as against the the hydrological system and sound conventional in situ flood studies that are sustainable management of natural peculiar to developing countries such as resources and the environment. Nigeria. In Nigeria, flood usually occurs in In Nigeria, studies on flood have been form of coastal flood, river flood, flash limited to flood hazard flood, urban flood, dam failure-induced modeling/mapping, exposure and flood and ecological release flood vulnerability analysis (Komolafe et al., (Komolafe et al., 2015). Among these, 2015). Also, study site is usually limited flash flood and urban flood are the to settlement boundary and flood disaster commonest and the most frequent, which impacted area. Moreover, studies on have become seasonal occurrences in flood would better be based on an entire many Nigeria’s settlements. The first drainage basin. This is because; the incidence of urban flood came up 1948 in tendency of flood event occurring in a 230

Ethiopian Journal of Environmental Studies and Management Vol. 10 no.2 2017 given location is a function of the hand, impervious surfaces such as built characteristics of the host basin and the up area and compacted bare ground are nature of its hydrological partitioning. usually characterized infiltration potential Thus, basin characteristics such as and high runoff, leading to high tendency morphometry and landuse have been towards flood occurrence. observed to have decisive influence on Overtime, basin characteristics basin’s hydrological partitioning vis-à-vis usually change in response to form- flood hazard (Ayandike and Phil-Eze, process interaction. In turn, these changes 1989; Pitlick, 1994; Ifabiyi, 2004; Jimoh also determine the nature of and and Iroye, 2009). For instance, variability of hydrological partitioning to morphometric parameters such as a great extent. Thus, there is the need to Elongation Ratio, Form Factor and investigate basin characteristics Circularity Ratio could give meaningful periodically at different levels of order explanation to potential response of a (Ajibade et al., 2009). This would given basin to sudden rainstorm. In this provide a lead to how hydrological case, an elongated basin would be challenges could be adequately tackled characterized by short concentration time within a basin. This study therefore, (leading to faster rise in channels’ water attempts to investigate the environmental level) but low and extensive peak characteristics of some selected drainage discharge. Also, parameters such as basins with a view to understanding the Length of Overland Flow, Drainage impact of basin conditions on the Density, Drainage Texture and exposure of human settlements to flood Infiltration Number would give an insight hazards. to runoff characteristics of a given basin. Study Area Thus, high Drainage Density, low Length In this study, five (5) sub-basins were of Overland Flow and high Infiltration investigated in Osun Watershed, central Number are all indicators of potential Southwestern Nigeria (Figure 1). The high runoff, which invariably could result basins are located within 7 o 49' N, 4 o 30' to flooding. E and 7 o 34' N, 5 o 00' E, in the tropical Studies have revealed that vegetation rainforest region of Southwestern usually play a significant role in Nigeria. The studied sub-basins host the hydrological partitioning (Ifabiyi, 2004; two largest and most populous Jimoh and Iroye, 2009). For instance, settlements (Ilesa and Osogbo thick vegetation (such as forest) usually Metropolis) in Osun Drainage Basin. intercepts rainwater and thus, retards the Ilesa and Osogbo Metropolis (in Osun rate of surface accumulation of rainwater. State) have been confronted with Likewise, plants play a significant role in numerous flood disasters since year 2000 evapotranspiration, which usually and flooding has become an annual event account for larger percentage of water particularly in the latter. Ilesa town is vapor in the earth atmosphere. Also, a situated within two (Ilesa and Iwaraja) sizeable volume of water are usually been drainage basins. Flash flooding is locked up in plant tissues. Vegetation common within Ilesa basin particularly also retards the formation of surface along the banks of its main channel and runoff on forest floor, thus reducing flood flood plain. But in the recent time, flood hazard and soil erosion. On the other events have been kept under control in 231

Morphometric and Landuse Analysis: Implications on Floo d Hazards ...... AKINWUMIJU, A.S.

Ilesa town. Osogbo metropolis (Capital these settlements is connected to the of Osun State) extends mainly across similarity in their climatic conditions and three (Olupona, Osogbo I and Osogbo II) the role they play as the major drainage basins in the low-lying area of commercial, industrial and cultural Osun Watershed. Annually, high density centers of Osun State, Southwestern area of Osogbo metropolis is usually Nigeria. A notable and most devastating inundated by flood water in response to flood disaster struck both settlements in thunderstorms and torrential rainfall at 2012, leading to loss of many lives and the peak of raining season. The choice of properties (Komolafe et al., 2015).

Figure 1: Map of the Study Area showing a): Nigeria’s State Boundaries; b): Studied Sub - The climate of the studied drainage basin (between 1,650 and 1,700 mm per basins is characterized by a long rainy annum) and the only dry months are season from March/April through to January and February. Relative humidity October. The study area lies within the rarely dips below 60% and fluctuates Humid Tropical Climatic Zone that between 75% and 90% for most of the normally experience double maximal year (Orimoogunje et al., 2009). During rainfall that peaks in July and October. the peak period of the rainy season, cloud Precipitation is uniformly high across the cover is nearly continuous resulting in 232

Ethiopian Journal of Environmental Studies and Management Vol. 10 no.2 2017 mean annual sunshine hours of 1,600 and technique of unsupervised (maximum an average annual temperature of likelihood) classification was adopted to approximately 28 oC.Air quality in the generate landuse map for the sub-basins. study area is generally good, although Classification was based on six (6) minor industrial activities and different landuse classes that were identified on forms of road traffic have increased in the satellite imagery and confirmed by recent years particularly within the urban field investigations. Quantitative centers leading to the formation of urban statistical analyses of the classification heat island in Osogbo metropolis results were undertaken. To complement (Babatola, 2013). the morphometric and landuse analysis, Deciduous rainforest of the study area lithology of the basin was analyzed. All can further be sub-divided into three analyses were undertaken in ArcGIS types. These include the disturbed 10.4.1 environment. In order to achieve rainforest, the light forest and the patches the aim of this study, all the basin of thick forest. The disturbed rainforest is characteristics were comparatively the anthropogenic impacted rainforest evaluated. with many randomly distributed open spaces as a result of human activities Results such as agriculture, mining, lumbering The computed basin parameters are and fuel wood harvesting. The light presented in Table 3. Sixty percent of the forest is emerging forest at the stage of basins are drained by 4 th order river secondary succession that is common on network while the remaining 40 percent the slightly weathered rocks. The patches are drained by 3 rd order river network. of thick forest are the few natural Basin Area ranges from 97.28 km 2 to rainforests of the Southwestern Nigeria 5.90 km 2 with the highest and lowest that are relatively protected from values recorded for Iwaraja and Osogho encroachment. These include the forest II respectively. The highest and the reserves and traditionally preserved lowest Basin Perimeters are recorded for forests that are consecrated to some Ilesa basin and Osogbo II respectively. traditional religions and festivals in Mean Bifurcation Ratio varies from Yoruba Land. 2.84to 4.32 with the lowest value occurring in Ilesa and Osogbo I and the Methodology highest value occurring in Ilesa basin. Details of the data used in this study Bifurcation Ratio is highly variable in are presented in Table 1. Initial stage of Ilesa and Osogbo I compared to other the research involves the extraction of basins. Stream Number ranges from 12to river network for the sub-basins based on 90with length varying from 9.1 km to their boundaries as dictated by drainage 124.66 km. While the highest Stream divides. Strahler (1964) approach was Number and length are recorded for adopted to order the rivers of the basins. Iwaraja basin, the highest Mean Stream Twenty-three morphometric parameters Length is recorded for Ilesa basin. Stream were computed from DEM-based vector Frequency is high in Osogbo I and data for the sub-basins. The parameters Osogbo II (S f = 2.1 and 2.0 respectively) and corresponding formulae are and it is low in Olupona (Sf = 0.9), presented in Table 2. Image analysis Iwaraja (S f = 0.9 and Ilesa (Sf = 0.8). the 233

Morphometric and Landuse Analysis: Implications on Flood Hazards ...... AKINWUMIJU, A.S. highest Main Stream Length is recorded Cultivation ranges from 21.80 percent in for Ilesa (15.59 km) and lowest is the former to 0.06 percent in the latter. computed for Osogbo I (1.59 km). While 30.39 and 29.21 percent forest Length of Overland Flow ranged from cover occur within Iwaraja and Ilesa 0.31to 0.40 with the highest and the basins respectively, Olupona, Osogbo I lowest value occurring in Olupona and and Osogbo II are void of forest cover. Osogbo I respectively. The highest Basin The highest and lowest percentage of Length is recorded for Ilesa basin (19.88 rock outcrop occurs in Olupona (2.06) km) and the lowest is recorded for and Osogbo II (0.34) respectively. Osogbo II (4.32 km). Drainage Density The lithology of Iwaraja basin is ranges from 1.2 in Olupona and Iwaraja characterized by Banded Gneiss basins to 1.6 in Osogbo I. The highest (46.57%), Quartz Schist (26.46%), Drainage Texture is recorded for Osogbo Amphibole Schist (20.76%) and Granite I (2.12) while the lowest occurs in Gneiss (6.21%). Ilesa basin is Olopona basin (0.89). The highest and predominantly underlain by Amphibole lowest Channel Gradient is recorded for Schist (76%) with minor occurrence of Osogbo II (10.02 m/km) and Ilesa (3.61 Banded Gneiss (17.07%) and Quartz m/km) respectively. Maximum Basin Schist (6.93%). The lithology of Olupona Relief is highest in Iwaraja (282 m) and basin is dominated by Mica Schist lowest in Osogbo II (67 m). Infiltration (93.54%) with slight occurrence of Number ranges from 3.53 in Osogbo I to Banded Gneiss (6.46%). While Mica 1.16 in Iwaraja. Relief Ratio varies from Schist and Banded Gneiss occur almost at 0.95 in Iwaraja to 0.18 in Osogbo I. equal proportion (56.36% and 43.64% Basin Slope is high in Iwaraja (0.0177), respectively) in Osogbo I basin, the latter Osogbo II (0.0155) and Olupona (0.0113) dominates the lithology of Osogbo II while Osogbo I and Ilesa have low Basin basin (underlying 98.64% of the basin) Slope (Bs = 0.0097 and 0.0091 with slight representation of the former respectively). Form Factor varies from (1.36%). In crystalline form, 0.38 in Iwaraja to 0.21 in Ilesa while the metamorphic rocks are characterized by highest and lowest Elongation Ratio is low porosity and absorption capacity. recorded for Iwaraja (0.20) and Ilesa However, their porosity could be (0.15) respectively. Circularity Ratio (Rc) enhanced by tectonic activities such as ranges from 0.56 in Iwaraja to 0.35 in fracturing, faulting and shearing. Basin Ilesa with 80 percent of the studied orientation is NE-SW in Olupona (239 o), basins having Rc values in excess of 0.5. Osogbo I (228 o) and Osogbo II (249 o) The highest and the lowest Compactness while Iwaraja (134 o) and Ilesa (124 o) Coefficient are computed for Ilesa (1.69) have SE-NW orientation. and Olupona (1.31) respectively. Texture Ratio ranges from 1.65 in Osogbo I to Discussion 0.63 in Olupona. Although all the basins are elongated, The percentage Built-Up Area ranges Ilesa basin is more elongated. As from 89.40 in Osogbo II to 24.54 in indicated by the computed values of Iwaraja. Intensive Rainfed Agriculture Elongation Ratio, Form Factor, varies from 21.93 percent in Iwaraja to Circularity Ratio and Compactness 10.20 percent in Osogbo II and Shifting Coefficient, water level in the main 234

Ethiopian Journal of Environmental Studies and Management Vol. 10 no.2 2017 channel of Ilesa basin will quickly and Olupona basins are dominated by respond to sudden heavy storm compared impervious surface with patches of to other basins (Miller, 1953; Gregory farmlands and outright absence of forest and Walling, 1973; Ifabiyi, 2004; cover. Results show that substantial Ajibade et al., 2010; Akinwumiju and percentages of Iwaraja and Ilesa basins Olorunfemi, 2016). However, peak are covered by forest while large parts of discharge will be low by being extended the basins constitute agricultural over a much longer period of time in landuses. Rocky outcrop is poorly Ilesa basin (Jimoh and Iroye, 2009). represented across all the basins, Thus, floods are much easier to manage indicating advanced weathering stage and within Ilesa basin compared to other occurrence of relatively thick soil profile basins (Strahler and Chow, 1964; Hajam (Akinwumiju, 2015). The lithology of the et al., 2013). The computed values of Iwaraja and Ilesa basins is dominated by Bifurcation Ratio show that Osogbo II, meta-sedimentary and meta-igneous Osogbo I and Olupona basins are prone rocks with substantial occurrence of old to flood hazards (Schumn, 1956; Rakesh granitic rocks while Olupona, Osogbo I et al., 2000). Likewise, results also and Osogbo II are predominantly indicate potential flood danger at the underlain by old granitic rocks that have upper part of Ilesa basin owing to low been subjected to intense metamorphism Bifurcation Ratio of the 2 nd order rivers. (Akinwumiju et al., 2016). Thus, Stream Frequency, Length of Overland overburden thickness and infiltration Flow, Drainage Density, Drainage potential vary with lithologic types across Texture and Mean Stream Length the basins (Akinwumiju, 2015). indicate that Osogbo I and Osogbo II are Implications on Flood Hazards in Ilesa more prone to flash flood compared to and Osogbo Metropolis other basins (Schmid, 1997; Akinwumiju Morphometric and landuse and Olorunfemi, 2016). The extremely characteristics of Iwaraja and Ilesa basins low Main Stream Length recorded for imply that exposure to flood hazards is Osogbo I suggest that the basin is highly relatively low in Ilesa town. However, exposed to flood hazard at its lower linear and relief characteristics of Ilesa course due to potential higher peak basin suggest possible occurrence of discharge and sudden rise in channel flash flood along its main channel. water level. Relief Ratio and Basin Slope Another reason for the relatively low indicate that sudden heavy storm will flood risk in Ilesa town is the occurrence result to swift rise in water level and of the heavily fissured quartz schist that prolong flood water retention in the main forms a ridge-like cuesta within Iwaraja channel of Osogbo I basin (Schumn, basin. The geologic unit has high 1956; Hajam et al., 2013). Infiltration absorbing capacity, thereby forming a Number suggests high runoff for Osogbo natural basin water discharge regulator I and Osogbo II due to relatively low and a prolific watershed that gives rise to infiltration potential, which cannot be many perennial rivers within the basin unconnected with high percentage of (Akinwumiju, 2015). The positioning of impervious surface (Jimoh and Iroye, Ilesa at the upstream of its host basins 2009; Hajam et al., 2013). Landuse could pose potential flood danger as analysis reveals that Osogbo II, Osogbo I urbanization extends downstream. This is 235

Morphometric and Landuse Analysis: Implications on Flood Hazards ...... AKINWUMIJU, A.S. because, the urbanized (impervious) hazards is relatively low in Iwaraja and upstream would lead to elevated peak Ilesa basins. However, results suggest discharges from lower order sub-basins high risk of flash flooding along the main due to reduced infiltration capacity channel of Ilesa basin. The observed low (Jimoh and Iroye, 2009). flood risk in Iwaraja basin is attributed to Based on the results of this study, it is the heavily fissured bedrocks that adjudged that Osogbo Metropolis is dominate the lithology of the basin. highly exposed to flood hazards as a Consequently, it was observed that result of unfavorable morphometric Osogbo Metropolis is highly exposed to characteristics and extremely high rate of flood hazards compared to Ilesa town urbanization of its host basins. This where potential flood dangers are easy to situation is further compounded by the manage. Landuse analysis indicate that absence of forest cover as well as high more than 85 percent of Osogbo I, rainfall intensity and duration. The Osogbo II and Olupona basins are built exposure of live and properties to flood up and thus, impervious; leading to hazards has been aggravated by the elevated peak discharge. On the other current overdevelopment of flood plains, hand, less than 32 percent of Iwaraja and wetland reclamation and channel Ilesa basins are built up while more than modification (Orimoogunje et al., 2009). 66 percent of these basins are covered by Also, uncontrolled urbanization has vegetation of varying degrees of rendered the entire host basins (Osogbo I, thickness, hence high infiltration. Osogbo II and Olupona) almost However, relief characteristics suggest completely impervious, meaning that possible occurrence of flash flood in Ilesa larger percentage of rainwater will town particularly along the banks of the eventually leave the basin as runoffs. Due main channel of Ilesa basin. Therefore, to shape and areal characteristics of the while the annual flood incidence in host basins, channel water level tend to Osogbo metropolis is connected to respond quickly to sudden rainstorm in overdevelopment of its host basins, the Osogbo Metropolis and the eventual occurrence of occasional flash flood in flood water would maintain its level for a Ilesa town can be attributed to the considerable period of time as a result of morphometric characteristics of its host its relief characteristics that favor faster basins. Thus, the need for all-inclusive concentration of rainwater to the main sustainable development is eminent, not channel but with reduced discharge rate. only within the examined basins, but across all Nigeria’s settlements. Conclusion Morphometric characteristics and Acknowledgement landuse of some basins were analyzed in The author is grateful to the order to understand flood hazards within anonymous reviewers for their Ilesa and Osogbo metropolis in Osun suggestions. The author acknowledges State, Nigeria. Thirty basin parameters the Office of the Surveyor-General of the were analyzed for the five drainage Federation, Nigeria for providing the basins. Results indicate that Osogbo I, DEM. Appreciation also goes to National Osogbo II and Olupona basins are prone Aeronautics and Space Administration, to flood hazards while exposure to flood USA for making satellite imageries 236

Ethiopian Journal of Environmental Studies and Management Vol. 10 no.2 2017 available online for users. Many thanks Akinwumiju, A.S., Olorunfemi, M.O. also go to ESRI, USA for giving free and Afolabi, O. (2016). Automated ArcGIS multiple user licenses to my Lineament Mapping from Remotely University. Sensed Data: Case Study Osun Drainage Basin, Southwestern References Nigeria. Journal of Science, Adedeji, O.H., Odufuwa, B.O. and 18(1): 177-201. Adebayo, O.H. (2012). Building Atedhor, G.O., Odjugo, P.A.O. and Uriri, Capabilities for Flood Disaster and A.E. (2011). Changing Rainfall and Hazard preparedness and Risk Anthropogenic-Induced Flood: Reduction in Nigeria: Need for Impacts and Adaptation Strategies Spatial Planning and Land in Benin City, Nigeria. Journal of Management. Journal of Geography and Regional Planning , Sustainable development in Africa, 4(1): 45-52. 14(1): 45-58. Ayandike, R.N.G. and Phil-Eze, R.C. Agbonkhese, O., Agbonkhese, E G., Aka, (1989). Runoff Response to Basin E.O., Joe-Abaya, J., Ocholi, M. and Parameters in Southwestern Adekunle, A. (2014). Flood Menace Nigeria. Annals of Geography , 71A in Nigeria: Impacts, Remedial and (1&2): 75 – 84. Management Strategies. Civil and Babatola, E.B. (2013). Socio-Economic Environmental Research , 6(4): 32- Consequences of Flood in Ilesa, 40. Osun State, Nigeria. Geo-Studies Ajibade, L.T., Ifabiyi, I.P., Iroye, K.A. Forum, 6: 84-93. and Ogunteru, S. (2010). Gregory, K.J. and Walling, D.E. (1973). Morphometric Analysis of Ogunpa Drainage Basin Form and Process: and Ogbere Drainage Basins, A Geomorphological Approach , Ibadan, Nigeria. Ethiopian Journal Edward Arnold, London, 456pp. of Environmental Studies and Hajam, R.A., Hamid, A, and Bhat, S. Management , 3(1): 13-19. (2013). Application of Akinwumiju, A.S. (2015). GIS-Based Morphometric Analysis for Geo- Integrated Approach to Hydrological Studies Using Geo- Groundwater Potential Assessment Spatial Technology –A Case Study of Osun Drainage Basin, of Vishav Drainage Basin. Hydrol Southwestern Nigeria. An Current Res . 4: 157. Unpublished Ph.D. Thesis doi:10.4172/2157-7587.1000157 Submitted to the Institute of Ifabiyi, I.P. (2004). A Reduced Rank Ecology and Environmental Model of Drainage Basin Response Studies, Obafemi Awolowo to Runoff in Upper Kaduna University, Ile-Ife, Nigeria. 316pp Catchment of Northern Nigeria. Akinwumiju, A.S. and Olorunfemi, M.O. Geo-studies Forum , 2(1): 109-117 (2016). Morphometric Analyses of Ijigah, E.A. and Akinyemi, T.A. (2015). Osun Drainage Basin, Southwestern Flood Disaster: An Empirical Nigeria. Journal of Geography and Survey of Causative Factors and Geology , 8(4): 9-22. Preventive Measures in Kaduna, Nigeria. International Journal of 237

Morphometric and Landuse Analysis: Implications on Flood Hazards ...... AKINWUMIJU, A.S.

Environment and Pollution Pitlick, J. (1994). Relations between Peak Research , 3(3): 53-66. Flows, Precipitation and Jimoh, H.I. and Iroye, K.A. (2009). Physiography for Five Mountainous Managing High Runoff Discharge Regions in Western U.S.A. Journal in the Urbanized Basins of Asa of Hydrology , 158: 219 – 240. River Catchment Area of , Rakesh, K., Lohani A.K., Sanjay C.C. Nigeria. Environmental Research and Nema R.K. (2000). GIS based Journal , 3(2): 25-34. morphometric analysis of Ajay Komolafe, A.A., Adegboyega, S.A. and river basin up to Sararath Gauging Akinluyi, F.O. (2015). A Review of Site of South Bihar. J. Appl. Flood Risk Analysis in Nigeria. Hydrol., 14: 45-54. American Journal of Environmental Schmid, B.H. (1997). Critical Rainfall Sciences , 11(3): 157-166. Duration for Overland Flow an Miller, V.C. (1953). A Quantitative Infiltrating Plane Surface. Journal Geomorphic Study of Drainage of Hydrology, 193: 45-60. Basin Characteristics in the Clinch Schumn, S.A. (1956). Evolution of Mountain Area, Virginia and drainage systems and slopes in Tennessee. Department of Geology, badlands at Perth Amboy, New Columbia University. Jersey. Geological Society of Olawuni, O.P., Popoola, A.S., Bolukale, American Bulletin, 67: 597-646. A.T., Eluyele, K.P. and Adegoke, Strahler, A.N. and Chow V.T. (1964). J.O. (2015). An Assessment of the Quantitative geomorphology of Factors Responsible for Flooding in drainage basins and channel Ibadan Metropolis, Nigeria. Journal network, In. Handbook of Applied of Environment and Earth Sciences , Hydrology , McGraw Hill Book 5(21): 1-7. Company, New York, USA Orimoogunje, O.O.I., Oyinloye, R.O. and Strahler, A.N. (1964). Quantitative Momodou, S. (2009). Geospatial Geomorphology of Drainage Basins Mapping of Wetlands Potential in and Channel Networks. In: V.T. Ilesa, Southwestern Nigeria. FIG Chow (Ed.). Handbook of Applied Working Week, Surveyors Key Role Hydrology . McGraw-Hill, New in Accelerated Development , Eilat, York, pp. 439-476. Israel.

Table 1: Base Data and their Sources

238

Ethiopian Journal of Environmental Studies and Management Vol. 10 no.2 2017

Table 2: Morphometric Parameters and Formula

\

239

Morphometric and Landuse Analysis: Implications on Flood Hazards ...... AKINWUMIJU, A.S.

Table 3: Physiographic and Landuse Attributes of the Basins

240