Geomorphology of Mandvi to Mundra Coast, Kachchh, Western India

Abstract

Abstract. Landforms of coast between Mandvi and Mundra in Kachchh and their origin are described here. Various micro-geomorphic features such as delta, beaches (ridge & runnel), coastal dunes, tidal flat, tidal creek, mangrove, backwater, river estuary, bar, spit, saltpan etc. are explained. The delta sediment of Phot River is superimposed by tidal flat sediments deposited later during uplift in last 2000 years. Raise-beach, raise-tidal flat, firm sub-tidal mud pockets on beach, delta and parabolic dune remnants and palaeo-fore dune (Mundra dune) -all these features projects 3 to 4 m high palaeo-sea level than the present day. All these features are superimposed by present day active beach, dune, tidal flat, creek, spit, bar, lagoon, estuary and mangroves. All these are depositional features.Keywords: Coastal Geomorphology, mandvi, mundra, kachchh, landforms. IntroductionThe micro-geomorphic features, their distribution and origin in Mandvi to Mundra segment of Kachchh are described here. Tides, waves and currents are common coastal processes responsible for erosion, transportation and deposition of the sediments and produce erosional and depositional landform features in the study area. Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth. Most places in the ocean usually experience two high tides and two low tides each day (semi-diurnal tide), but some locations experience only one high and one low tide each day (diurnal tide). The times and amplitude of the tides at a locale are influenced by the alignment of the Sun and Moon, by the pattern of tides in the deep ocean and by the shape of the coastline and near-shore bathymetry. The study area is affected by semi-diurnal tidal cycles. Almost half of the study area is tide dominated. While tides are usually the largest source of short-term sea-level fluctuations, sea levels are also subject to forces such as wind and barometric pressure changes, resulting in storm surges, especially in shallow seas and near coasts.Wind waves or, more precisely, wind-generated waves are surface waves that occur on the free surface of seas and oceans. They usually result from the wind blowing over a vast enough stretch of fluid surface. Wind waves range in size from small ripples to huge waves over 30 meters high. Wind waves in the ocean are called ocean surface waves. As waves travel from deep to shallow water, their shape alters (wave height increases, speed decreases, and length decreases as wave orbits become asymmetrical). This process is called shoaling. The great majority of large breakers one observes on a beach result from distant winds. Five factors influence the formation of wind waves which work together to determine their size: 1. Wind speed, 2. Distance of open water that the wind has blown over (called the fetch), 3. Width of area affected by fetches, 4. Time duration the wind has blown over a given area, 5. Water depth.Some waves undergo a phenomenon calle...