Geo-Meteorological Hazards and Risk

This chapter discusses geo-meteorological hazards such as floods, landslides, and earthquakes in their interlined consequences. The flood risk rating map of the channel reveals that higher values exist in River Chel and in accordance the flood susceptibility map also denotes the same. The downstream sections of River Chel near Rajadanga and Kranti Lataguri are mostly affected by flooding. It is the downstream section after Gajoldoba barrage over River Teesta. The landslide susceptibility map and earthquake events of the entire area with “b” value analysis disclose and specify hazardous instability of the area. The flood inundation is accompanied by bank erosion in the area downstream of the bridge because of the increased average velocity below the constricted section, flow divergence, and increased shear stress, which put pressure on the highly sandy bank materials. The zones or sections of River Chel that may be at risk of flooding are therefore identified as a result of the bridges’ construction based on factors such as depth, velocity, manning, and debris factor. A physical model using potassium permanganate is then used to visualize the effect downstream on the bridge, which has a tendency to flow along the banks and increase the shear stress on the bank.