University of Ghana http://ugspace.ug.edu.gh SEDIMENT YIELD AND BANK EROSION ASSESSMENT OF PRA RIVER BASIN BY John Manyimadin Kusimi (10096985) This thesis is submitted to the University of Ghana, Legon in partial fulfilment of the requirement for the award of PhD Geography & Resource Development degree. June, 2014 University of Ghana http://ugspace.ug.edu.gh Declaration This thesis entitled “Sediment yield and bank erosion assessment of Pra River Basin” is entirely an original study that I conducted. With the exception of relevant literature and ideas of specific sources which have been duly referenced, the work has not been presented anywhere in part or whole for any award of a degree. ........................................................ John Manyimadin Kusimi (Student) (10096985) Date........................................... ............................................................ Dr. Emmanuel Morgan Attua Dept of Geography & Resource Dev’t University of Ghana, Legon (Principal supervisor) Date........................................... ........................................................ Prof Bruce Banoeng-Yakubo Department of Earth Science University of Ghana, Legon (Supervisor) Date........................................... ............................................................... Dr. Barnabas Amisigo Water Research Institute CSIR, Accra (Supervisor) Date........................................... i University of Ghana http://ugspace.ug.edu.gh DEDICATION This work is dedicated to my family for their immense support, prayers and contribution. ii University of Ghana http://ugspace.ug.edu.gh Acknowledgement I am grateful to God for bringing me this far in life and academia; to my supervisors: Dr. Emmanuel Morgan Attua, Dr. Barnabas Amisigo and Prof Bruce Banoeng-Yakubo for their support, suggestions, patience and making time off their busy schedules to supervise my work. The University of Ghana partially funded this thesis by awarding me a Faculty Development Grant which was very helpful in undertaking the field work and meeting the costs of field data analysis. I will like to express my gratitude to my brother Jonathan Kusimi, wife Mrs. Bertha Kusimi and Mr. Gabriel Appiah of Water Research Institute, CSIR – Accra for assisting me in my field data collection. I will wish to thank Water Research Institute, CSIR - Accra and Ecological Laboratory (ECOLAB) of the Dept of Geography & Resource Development, University of Ghana for providing field equipment and laboratory space to collect and analyze my field samples. The support of Mr. Prince Owusu of ECOLAB during my field data analyses is also acknowledged. Lastly, I wish to thank Mr. Gerald B. Yiran of the Dept of Geography & Resource Development, University of Ghana for always responding to my call anytime I was in need of assistance with respect to data processing and analysis on the modelling aspect of the thesis. iii University of Ghana http://ugspace.ug.edu.gh List of Tables Table Page Table 2.1: Examples of models for the derivation of R values................................... 34 Table 3.1: Discharge Rating Curves............................................................................ 42 Table 3.2: Annual suspended sediment load and specific suspended sediment yield for the monitored stations in the Pra River Basin................................................ 56 Table 3.3: Parameters for suspended sediment rating curves....................................... 57 Table 4.1: Mean 210Pb Concentration levels for stream sediment and potential source materials in Birim Basin........................................................................... 64 Table 4.2: Mean 210Pb Concentration levels for stream sediment and potential source materials in Pra Basin............................................................................... 64 Table 4.3: Mean 210Pb Concentration levels for stream sediment and potential source materials in Oda Basin............................................................................. 64 Table 4.4: Mean 210Pb Concentration levels for stream sediment and potential source materials in Offin Basin............................................................................ 64 Table 4.5: Contribution of bank material and surface soil sources to suspended sediment load in the various sub-catchments...................................................... 64 Table 5.1: Annual bank erosion or deposition rates at Anyinam................................. 75 Table 5.2: Annual bank erosion or deposition rates at Amuanda Praso....................... 75 Table 5.3: Annual bank erosion or deposition rates at Akim Oda.............................. 76 Table 5.4: Annual bank erosion or deposition rates at Brenase.................................. 76 Table 5.5: Annual bank erosion or deposition rates at Ejisu....................................... 76 Table5.6: Annual bank erosion or deposition rates at Adiembra................................ 77 iv University of Ghana http://ugspace.ug.edu.gh Table 6.1A: K Factor Values of the Soil types............................................................. 86 Table 6.1B: Soil erodibility classification.................................................................... 86 Table 6.2: Land Cover Types and Cover Management (C) factor values.................... 88 Table 6.3: Attributes of Landsat ETM+ 2008............................................................. 88 Table 6.4: Land cover co-efficient values................................................................... 90 Table 6.5: Statistics of the different sediment yield model variables......................... 100 Table 6.6: Estimates of sensitivity analysis of sediment yield for 12 mm event......... 101 Table 6.7: Estimates of sensitivity analysis of sediment yield for 12.5 mm event....... 101 List of Figures Figure Page Fig.1.1: Map of the Pra River Basin........................................................................... 14 Fig.3.1: Sediment Yield Sampling Stations................................................................ 40 Fig.3.2: Daily mean concentration of samples at Anwiankwanta.............................. 44 Fig.3.3: Daily mean concentration of samples at Brenase........................................... 44 Fig.3.4: Daily mean concentration of samples at Akim Oda....................................... 45 Fig.3.5: Daily mean concentration of samples at Adiembra....................................... 45 Fig.3.6: Daily mean concentration of samples at Twifo Praso.................................... 46 Fig.3.7: Daily mean concentration of samples at Assin Praso.................................... 46 Fig.3.8: Daily mean concentration of samples at Sekyere Heman.............................. 47 Fig.3.9: Mean monthly sediment load at Akim Oda................................................... 50 Fig.3.10: Mean monthly sediment load at Brenase..................................................... 50 Fig.3.11: Mean monthly sediment load at Anwiankwanta......................................... 51 v University of Ghana http://ugspace.ug.edu.gh Fig.3.12: Mean monthly sediment load at Adiembra.................................................. 51 Fig.3.13: Mean monthly sediment load at Twifo Praso.............................................. 52 Fig.3.14: Mean monthly sediment load at Assin Praso............................................... 52 Fig.3.15: Mean monthly sediment load at Sekyere Heman......................................... 53 Fig.3.16: Annual sediment yield. ............................................................................... 56 Fig.5.1: Particle size distribution curves of bank sediments....................................... 80 Fig.5.2: Eroded bank sediments.................................................................................. 82 Fig.6.1: Schematic chart of GIS applications to soil erosion mapping and the derivation of Sediment Delivery Ratio, SDR.............................................................. 84 Fig.6.2: Effective total rainfall erosivity (Re) factor map of 2008 for 12 mm............ 92 Fig.6.3: Effective total rainfall erosivity (Re) factor map of 2008 for 12.5 mm......... 92 Fig.6.4: The soil erodibility (K) map of the basin........................................................ 92 Fig.6.5: The length and slope (LS) map of the basin................................................... 92 Fig.6.6: Cover management factor (C) map derived from satellite image classification....................................................................................................... 93 Fig.6.7: Soil erosion potential map of the basin.......................................................... 93 Fig.6.8: Gross soil erosion map of 12 mm erosive event............................................ 95 Fig.6.9: Gross soil erosion map of 12.5 mm erosive event......................................... 95 Fig.6.10: Sediment delivery ratio map of the basin................................................... 95 Fig.6.11: Sediment yield map of 12 mm erosive event.............................................. 95 Fig.6.12: Sediment yield map of 12.5 mm erosive event........................................... 96 vi University of Ghana http://ugspace.ug.edu.gh List of Plates Plate Page Plata1.1a: Illegal gold mining along the bank of the Birim River at Kyebi................... 8 Plata1.1b: Illegal alluvial gold mining of the river bed and bank of the Ofin River at Adwumain..........................................................................................