5. Mining Response on Alluvial Channel Flow and Sediment Transport: Application of Hydro-Morphological Techniques and Principal Component Analysis (PCA)

Interruption of hydraulic variables (HVs) like flow and sediment regime has negative impact on bedload sediment transport (BLST). This chapter focuses on hydraulic response on bedload and mining intensity in river Kangsabati and also tries to determine the effects of mining intensity on BLST with the presence of sub critical flow velocity, bed shear stress including shear velocity, bed roughness from sandbar to mining sites and pits in upper, middle and lower courses, respectively. Well known established hydraulic equations along with Ackers and White (J Hydraul Eng Div ASCE 99(hy11):204–254, 1973), Meyer-Peter and Muller methods (IAHSR 2nd meeting, Stockholm, appendix 2. IAHR, 1948) and Du Boys (Ann Ponts Chaussees 5(18):141–195, 1879) were used to derive the HVs of BLST in three different sites. Principal component analysis (PCA) and Prinsscore both are applied to derive the interruption of BLST caused by instream sand mining. Hydraulic formula demonstrated that most of the sediment trapping occurred in mining and pit sites of upper course caused by sub critical flow induced bed shear stress increased the bedload sediment transport while low bed roughness with large velocity increases the entrainment capacity but bedload transport abruptly decreases in sandbar sites. Turbulent flow induced shear stress increased the bedload transport in sandbar sites of middle course while hungry water affected shear velocity increased the transport capacity but low shear stress decreases the bedload transport; thus huge sediments are trapped in pit sites of middle and lower course. PCA revealed the inverse changes of HVs to lead more instability in channel morphology of mining and pit sites than sandbar.