Pratap Kumar Mohanty

Impact of Groins on Beach Morphology: A Case Study near Gopalpur Port, East Coast of India

Abstract MOHANTY, P.K.; PATRA, S.K.; BRAMHA, S.; SETH, B.; PRADHAN, U.; BEHERA, B.; MISHRA, P., and PANDA, U.S., 2012. Impact of groins on beach morphology: a case study near Gopalpur Port, east coast of India. Gopalpur Port is being developed as an all-weather open seaport from a fair-weather port which has existed since 1987. Two groins, a 530-m south groin and a 370-m north groin, were constructed during the periods from August 2007 to November 2009 and October 2007 to September 2008, respectively, on the north and south of the 500-m jetty which existed earlier. Port authorities are planning to construct a southern breakwater and a series of seven northern groins. Therefore, it is essential to assess the impacts of coastal structures on beach morphology and shoreline change in the present context and to predict future trends. To achieve this, a long-term observational programme has been conducted since May 2008. Observations include beach profile, shoreline change (berm position), littoral environment observations, and sedimentological characteristics at monthly intervals north and south of the port, covering a total distance of about 5 km. From the analysis of results, erosion is observed north of the northern groin, particularly during the monsoon season. From October to January, deposition is observed mostly in the foreshore which replenishes the erosive environment observed during monsoon. On the other hand, a constant depositional trend is noticed south of the southern groin for 1.5 km. To assess the impacts of the present groins, beach profile and sediment characteristics were compared with observations made from February 2002 to February 2003. The comparison distinctly shows the impact of groins on erosion and deposition on the north and south beaches of the port. Volume, beach width, and beach area estimates indicate that the rate of deposition on the south beach is much faster than the rate of erosion on the north.

Monitoring and Management of Environmental Changes along the Orissa Coast

Abstract Orissa, the maritime state along the east coast of India, has a coastline of 480 km. The southern part of the coast has a narrow shelf, but the north Orissa coast has an extended continental shelf. The coastline is bestowed with six major estuaries, Indias second largest mangrove forest (Bhitarkanika Sanctuary), Asias largest brackish water coastal lagoon (Chilika), extensive sandy beaches rich in heavy minerals, the worlds largest rookery for the Olive Ridley sea turtle (Gahirmatha sandy beach within Bhitarkanika sanctuary), and two species of horseshoe crabs. In the last few decades there has been tremendous pressure on the coastal zone for the development of fisheries, aquaculture, ports, harbours, and urban settlements. These developments have led to environmental changes, some of which are irreversible, and thus have become issues of concern for the public as well as the state government. Some of the important environmental changes taking place, and which seriously affect the economy of the region, are tropical cyclones and associated storm surges, floods, decline in mangrove forests, accelerated shoreline changes, and transformation of the coastal lagoon ecosystem. This paper documents different coastal environmental features and their changes, observed during the last few decades through secondary data, field surveys, and remote sensing observations, and suggests a framework for a coastal zone management programme in the state.

Impacts of ENSO and IOD on tropical cyclone activity in the Bay of Bengal

Abstract The impacts of El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) on tropical cyclone (TC) activity (intensity, frequency, genesis location, track and average lifetime) in the Bay of Bengal (BoB) are studied for the period 1891–2007 using cyclone e-Atlas of India Meteorological Department, Niño3.4 Index, Oceanic Niño Index and Dipole Mode Index (DMI). TCs in the present study include cyclones with maximum sustainable wind (MSW) ≥34 knots (referred as cyclonic storms) and severe cyclonic storms with MSW ≥48 knots. The study shows a total of 502 TCs over BoB during the 117-year study period at the rate of 4.29 TC per year. Seven-year running mean of TCs for the period 1891–2007 shows a decreasing trend. Correlation between Niño3.4 Index and DMI for the 117-year period is significant and positive and the significance level is higher (lower) for the period with higher (lower) TC frequencies. One-third monthly interval analysis for the 117-year period indicates first third (1–10) of November as the most favoured period of TC formation over BoB. 117-year study period is divided into years of ENSO (El Niño, La Niña and neutral ENSO) and IOD (+ve IOD, −ve IOD and no IOD) categories. Maximum frequency of TC is observed during La Niña years, −ve IOD years and also when La Niña co-occurred with −ve IOD. More severe cyclones are formed during La Niña and +ve IOD years. Genesis location of TCs indicates that during La Niña (El Niño) years, the TCs are oriented in the south-east–north-west (south-west–north-east) direction. TCs in no IOD and −ve (+ve) IOD years are more (less) in northern BoB (north of 15° N), while in southern BoB (south of 15° N), TCs are more (less) during no IOD and +ve (−ve) IOD condition. BoB is divided into four quadrants, and number of TCs in each quadrant is computed under different ENSO–IOD events. Peak direction of track movement is observed as north-east followed by north–north-west which is corroborated from the dissipation of TCs in the specific quadrant. Total TC tracks in the peak direction of track movement are maximum during El Niño and no IOD years. The study reveals that TCs with shorter lifetime are observed during El Niño and −ve IOD years, while TCs with longer lifetime are observed during La Niña, neutral ENSO and +ve IOD years. The decade with maximum TC formation is observed as 1921–1930, and the impacts of ENSO and IOD on decadal variability are distinctly observed.

Alongshore Sediment Transport Near Tidal Inlets of Chilika Lagoon; East Coast of India

ABSTRACT Chilika, a lagoon along the east coast of India, is undergoing transformation due to frequent shoreline change near inlet(s). Shoreline change near inlet includes change in position and shape of inlet, inlet channel length, and spit growth/erosion. These variable features of lagoon inlet(s) critically depend on alongshore sediment transport (LST) and discharge (water and sediment) from the lagoon to the sea. The LST and the processes responsible for sand spit growth/erosion, considered as important attributes of inlet stability, are the subject matter of the present investigation and hence the study assumes importance. The study includes integration of observational and modeling framework. Observations include nearshore wave, bathymetry, beach profile, shoreline and sediment grain size of spits while numerical modeling includes simulation of the wave using MIKE 21 Spectral Wave model and LST simulation using LITtoral DRIFT. The results indicate that the predominant wave directions as S and SSE, which induces round the year south to north alongshore transport with significant seasonal variation in magnitude. The estimated LST closely matches with previous studies near Chilika inlet and for other locations along the Odisha coast. Besides temporal variability, the study reveals spatial variability in alongshore transport near Chilika inlet and considers it as one of the important attributes along with northward spit growth for inlet migration/closure/opening.

Sediment Dispersion in the Bay of Bengal

The Bay of Bengal is about 2090 km long and 1610 km wide, bordered on the west by Sri Lanka and India, on the north by Bangladesh, and on the east by Myanmar (earlier Burma) and Thailand. The Andaman and Nicobar Islands separate it from the Andaman Sea, its eastern arm. The Bay of Bengal and the Andaman Sea are together defined as the oceanic area north of 5°N, bordered by the Indian subcontinent, Myanmar, Thailand, Malay Peninsula and Sumatra (Fig. 1). This unique semi-enclosed basin experiences seasonally reversing monsoons and depressions, severe cyclonic storms (SCS), and consequently receives a large amount of rainfall and river run-off in the tropics. It also encounters the largest seasonal sea level fluctuations (−40 cm to +54 cm) anywhere on the earth. An interesting characteristic of this area is its low saline surface water caused by large river run off from the Indian subcontinent and Myanmar. The circulation and hydrography of the Bay of Bengal is complex due to the interplay of semi-annually reversing monsoonal winds and the associated heat and freshwater fluxes. Apart from this, the inflow of warm high saline waters of the Arabian Sea, the Persian Gulf and the Red Sea origin and a number of synoptic disturbances (cyclones) originating during both pre-monsoon (May) and post-monsoon (October) period also affects the dispersal pattern in the Bay of Bengal. The impacts of the enormous discharge of riverine fresh water and sediments are least understood.

Mapping Lagoonal Features and Their Variability: Field Observations and Remote Sensing Implications

Lagoons have been historically important as sheltered sites of habitation providing access to both the land and the sea, comprising 15% of the world coastal zone, in which lakes, salt marshes, tropical mangroves, swamps and deltas are also included. Natural changes resulting from physical, chemical, geological, and biological factors and the influence of climatic changes will alter the essential character of the lagoon and hence the ecosystem. For example, excessive runoff due to flood during heavy rainfall may cause a chain of events like increase in sediment load leading to turbidity which tends to reduce sunlight penetration which in turn gives rise to lowered primary productivity. Long term unpredictable climatic variations such as tidal waves, hurricanes, cyclonic storms might also cause irreversible changes through sediment loading, alteration of flushing rates of lagoons and production processes (Fisher et al., 1972). So it is important that the maximum benefit from these areas be obtained without jeopardizing the future options or continued use.