Development of Tide–Surge Interaction Model for the Coastal Region of Bangladesh     

Gour Chandra Paul  Ahmad Izani Md. Ismail  Azizur Rahman  Md. Fazlul Karim  Ashabul Hoque 《Estuaries and Coasts》2016,39(6):1582-1599

In this paper, a two-dimensional, vertically integrated hydrodynamic model is developed taking into account entrained air bubbles during storm surges as well as incorporating inverted barometer, and river and land dynamics. The model is specifically designed for the coastal region of Bangladesh. A nested scheme method with a fine mesh scheme (FMS), capable of incorporating the complex coastline and all major offshore islands accurately, nested into a coarse mesh scheme (CMS) covering up to 15° N latitude in the Bay of Bengal is used. To incorporate the small and big offshore islands in the Meghna estuarine region with its complex coastline accurately, a very fine mesh scheme (VFMS) is again nested into the FMS. Along the northeast corner of the VFMS, the Meghna river discharge is taken into account. The coastal and island boundaries are approximated through proper stair steps. The model equations are solved by a semi-implicit finite difference technique using a staggered C-grid. A stable appropriate tidal condition over the model domain is generated by applying tidal forcing with the four major tidal constituents M ₂, S ₂, K ₁, and O ₁ along the southern open boundary of the CMS. This tidal regime is introduced as the initial state of the sea for nonlinear interaction of tide and surge. The model is applied to simulate water levels due to the interaction of tide and surge associated with the cyclones April 1991 and Aila at different coastal and island locations along the coast of Bangladesh. The results are found to be quite satisfactory with root mean square error of ～0.50 m as calculated for both the storm events. Tests of sensitivities on water levels are carried out for air bubbles, offshore islands, river discharge, inverse barometer, and grid resolution. The presence of air bubbles increases simulated water levels a little bit in our model, and the contribution of air bubbles in increasing water level is found around 2 %. Further, water levels are found to be influenced by offshore islands, river discharge, inverse barometer as well as grid resolution.  相似文献   

Role of hydrological regime and floodplain sediments in channel instability of the Bhagirathi River,Ganga-Brahmaputra Delta,India     

Sanat Kumar Guchhait  Aznarul Islam  Balai Chandra Das  Nishith Kumar Maji 《自然地理学》2016,37(6):476-510

Abstract

This research deals with the surface dynamics and key factors – hydrological regime, sediment load, and erodibility of floodplain facies – of frequent channel shifting, intensive meandering, and lateral instability of the Bhagirathi River in the western part of the Ganga-Brahmaputra Delta (GBD). At present, the floodplain of the Bhagirathi is categorized as a medium energy (specific stream power of 10–300 W m^?2), non-cohesive floodplain, which exhibits a mixed-load and a meandering channel, an entrenchment ratio >2.2, width–depth ratio >12, sinuosity >1.4, and channel slope <0.02. In the study area, since 1975, four meander cutoffs have been shaped at an average rate of one in every 9–10 years. In the active meander belt and sand-silt dominated floodplains of GBD, frequent shifting of the channel and meander migration escalate severe bank erosion (e.g. 2.5 × 10⁶ m³ of land lost between 1999 and 2004) throughout the year. Remote sensing based spatio-temporal analysis and stratigraphic analysis reveal that the impact of the Farakka barrage, completed in 1975, is not the sole factor of downstream channel oscillation; rather, hydrogeomorphic instability induced by the Ajay–Mayurakshi fluvial system and the erodibility of floodplain sediments control the channel dynamics of the study area.  相似文献   

Hydro-geophysical techniques for safe exploitation of the fresh groundwater resources in coastal area     

Sahebrao Sonkamble  Subash Chandra  V. K. Somvanshi  Shakeel Ahmed 《Environmental Earth Sciences》2016,75(4):279

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Hypsometric analysis of the micro-watersheds with different management practices located on Shivalik foothills     

Sushma Walia  Sarbjit Singh  Dikesh Chandra Loshali  Richa Babbar 《Arabian Journal of Geosciences》2018,11(11):276

In this paper, the hypsometric curves and integrals of four neighboring micro-watersheds draining into Patiala-Ki-Rao stream which is situated in the Shivalik foothills of district SAS Nagar in the Punjab state (India) has been presented to access and compare the erosion regimes under different management practices. Area-elevation ratio method has been used to compute hypsometric curve and integral values for each micro-watershed through ArcGIS 10.3 and Microsoft Excel. The 9-year data of runoff and sediment yield for all these micro-watersheds under different management practices has been analyzed for their effect on land cover and soil quality. Thus, the results of present study are very useful for comparing, planning, implementing, and controlling soil erosion in similar watersheds.  相似文献   

Geothermal energy potential of Tulsishyam thermal springs of Gujarat,India     

Hemant Kumar Singh  Aswathi Thankappan  Poonam Mohite  Satish Kumar Sinha  Dornadula Chandrasekharam  Trupti Chandrasekhar 《Arabian Journal of Geosciences》2018,11(6):137

Tulsishyam thermal springs are located in the Saurashtra region of Gujarat, India with discharge temperatures varying from 39 to 42 °C. The pH of these thermal springs varies from 7.1 to 7.4, indicating neutral character. Though these thermal springs propagate through the near surface layer of Deccan basalt, detailed geochemical analysis of the thermal waters using Piper diagram suggests that the water is interacting with the granitic basement rock. Silica and cation geothermometry estimates have reservoir temperature in the range of 138 to 207 °C categorizing it into a low to moderate enthalpy geothermal system. Furthermore, the area has high heat flow values of 53–90 mW/m² because of shallow Moho depth. The prevailing conditions suggest that the geothermal energy can potentially be exploited through an enhanced geothermal system (EGS). The study also indicates different mineral phases that may precipitate out of water during exploitation of geothermal energy and it should be taken into account while designing an EGS for the area.  相似文献   

Recession of Milam Glacier,Kumaun Himalaya,Observed via Lichenometric Dating of Moraines     

Kapil Bisht  Yogesh Joshi  Shashi Upadhyay  Poonam Metha 《Journal of the Geological Society of India》2018,92(2):173-176

Glaciers being very sensitive to climate change have been identified as one of the best indicators of climate change and evidences have proved that most of the Himalayan glaciers have receded with an increased rate during the recent past under the influence of global warming. Lichenometric study was carried out on the moraines of Milam glacier (located in Pithoragarh district of Uttarakhand) with the help of lichen species Dimelaena oreina having an average annual growth rate of 1.31 mm. The study revealed that Milam glacier has receded 1450 m in last 69.37 years with an average recession rate of 20.90 m/year. Since lichenometric studies are cost effective and ecofriendly in comparison to carbon dating, satellite and remote sensing based studies and also reliable, hence, it should be promoted in Himalaya which is an abode of glaciers.  相似文献   

Industrialisation in Fiji: Industrial structure and organisation     

Dr. Chandra Rojesh 《GeoJournal》1988,16(2):169-178

This paper analyses the significance, structure, and organisation of the manufacturing sector in Fiji, drawing on the author's earlier much larger study of industrialisation in Fiji. The latest Fijian census of industrial production (1984) and the author's 1983 survey of manufacturers in Fiji provide the main statistical basis of the study, which shows that the manufacturing sector is a moderately important component of the Fijian economy. It is dominated by resource industries, particularly food processing, but a wide range of manufacturing activities have, nonetheless, developed. There is a substantial number of small manufacturing establishments with a few large establishments, the latter, however, making an overwhelmingly important contribution to employment, gross output and value added. The market structure in the manufacturing sector is dominated by monopolies and oligopolies resulting from Fiji's small domestic market and its import substitution industrialisation strategy. There is an absence of informal sector activities in Fijian manufacturing, most firms being incorporated companies. The state has a major role as a direct producer in Fijian manufacturing. There are bound to be major changes in the manufacturing sector due to Fiji's current political crisis, but this paper does not address these because of the recency of the events and the consequent unavailability of relevant data.  相似文献   

Seasonal cycle of surface circulation in the coastal North Indian Ocean     

S R Shetye  S Satheesh Chandra Shenoi 《Journal of Earth System Science》1988,97(1):53-62

Monthly-mean winds and currents have been used to identify the driving mechanisms of seasonal coastal circulation in the North Indian Ocean. The main conclusions are: (i) the surface circulation off Arabia is typical of a wind-driven system with similar patterns of longshore current and wind stress; (ii) circulation off the west coast of India is consistent with the dynamics of a wind-driven eastern boundary current only during the southwest monsoon. During the northeast monsoon it is possible that the influence of the interior flow is important. (iii) There are at least three mechanisms that influence the surface circulation off the east coast of India: wind-stress, influence of fresh-water run off and contribution of the interior flow. It is difficult at present to assess the relative importance of these three processes.  相似文献   

Regional changes in food poverty in India     

Edison Dayal  Chandra Gulati 《GeoJournal》1993,30(2):167-177

Using average nutritive values of food actually consumed by individuals, this paper identifies regional concentration of hunger (food poverty) and its changes over time in rural India. There is clearly a heavy concentration of hunger in the coastal states of India, with few exceptions, which has persisted over time. Hunger has declined in about half the states of India but has increased in the remaining half. Unfortunately, it seems to have increased in the states that are relatively prosperous and are surplus producers of food. Hence, increased production of food, though important, does not necessarily reduce hunger. A redeeming conclusion of the study is that there has been a general improvement in the quality of food intake, particularly in the states where food poverty has declined.  相似文献   

SporadicE ionization associated with meteor events     

Girija Rajaram  H Chandra 《Journal of Earth System Science》1991,100(3):255-265

Two meteor events which were sighted in the Gujarat skies of India, were accompained by the visibility of sporadicE ionization on the ionograms recorded at Ahmedabad (Geog. Lat. 23·2°N, long. 72·30°E). The first event was the Dhajala fireball which flashed into the geoatmosphere along an E-N to W-S trail at about 20·40 h IST on 28 January 1976; the closest distance of the ground projection of meteor trail from Ahmedabad was 50km. The other event was a possible meteor group sighted over Ahmedabad on 28 May 1978, at about 21·10 h IST. This work describes the nature of the sporadicE ionization observed on Ahmedabad ionograms during the two events. Features of theEs echo during the Dhajala event which indicate that it could be of meteoric origin are discussed. Meteor theory is used to relate the observed ionization with the physical dimensions of the Dhajala meteorite as obtained by other workers.  相似文献