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In any effective landslide hazard mitigation plan, in-depth knowledge about the causes of instability is required. Consequently, it is essential to study geological, geotechnical, meteorological and anthropogenic factors that influence the landslide. For the present study a geophysical investigation has been carried out on a large landslide, on the slopes of Tertiary siltstones, mudstones, shales and sandstones at Atharamura Hill, Tripura. Different techniques have been used, including measurement of micro-slope using Total Station, clinometers and the LISCAD software for terrain modeling and determining the total volume of the material displaced and total area affected by landslides and analysis of soil properties to understand the present condition of the scarps. Results obtained through field investigation and laboratory testing revealed that the underlying cause of the slide could be (a) the adverse geological formation with unconsolidated sandy materials and occasional intersection of silt or clay layers, (b) the hydrological condition with continuous seepage through fractures, and (c) cutting of hill slopes for reconstructing and widening of the road (NH44). This latter anthropogenic influence has been triggered by an intense precipitation event during the monsoon season.

In this research work, an experimental investigation of wind effect on hexagonal cylinder was carried out. The study was performed on the single cylinder. The test was conducted in an open circuit wind tunnel at a Reynolds number of 4.22 x 10 4 based on the face width of the cylinder across the flow direction in a uniform flow velocity of 13.5 m/s. The test was carried out at various angles of attack from 0° to 50° at a step of 10°. The surface static pressures at the different locations of the cylinder were measured with the help of inclined multi-manometers. The wind velocity was kept constant at 13.5 m/s. The pressure coefficients were calculated from the measured values of the surface static pressure distribution on the cylinder. Later the drag and lift coefficients were obtained from the pressure coefficients by the numerical integration method. The results will enable the engineers and architects to design buildings more efficiently. Since the results will be expressed in the non-dimensional form they may be applied for the prototype building.

In this paper a new RS-GIS based simple method has been proposed for estimating bank erosion. This method does not need intense field investigation and can provide erosion vulnerability zonation for the entire river. The method uses eight parameters, i.e., rainfall erosivity, lithological factor, bank slope, meander index, river gradient, soil erosivity, vegetation cover, and anthropogenic impact. Meteorological data, GSI maps, SRTM DEM (30-m horizontal resolution), LISS III (23.5-m resolution), and Google Images have been used to determine rain erosivity, lithological impact, bank slope, meander index, river gradient, vegetation cover, and anthropogenic activities. Soil map of the NBSSLP (National Bureau of Soil Survey and Land-use Planning, India) has been used for assessing soil erosivity index. By integrating the individual values of those six parameters out of those eight parameters (the first two parameters remained constant for the particular study area), a bank erosion vulnerability zonation map of the River Haora, Tripura, India (23°37′–23°53′ N. and 91°15′–91°37′ E.) has been prepared. The values have been compared with the existing BEHI-NBS method of 60 spots and also with field data of 30 cross sections (covering the 60 spots) taken along a 51-km stretch of the river within Indian Territory, and we found that the estimated values are matching with the existing method as well as with field data. The whole stretch has been divided into five hazard zones, i.e. very high, high, moderate, low and very low hazard zones; and they are cover 5.66, 16.81, 40.82, 29.67, and 9.04 km, respectively.

In this research work, an experimental investigation of wind effect on pentagonal cylinders was carried out. The study was performed on the single cylinder in an open circuit wind tunnel at a Reynolds number of 4.22 x 104 based on the face width of the cylinder across the flow direction in a uniform flow velocity of 13.5 m/s. The test was carried out at various angles of attack from 0° to 63° at a step of 9°. The surface static pressures at the different locations of the cylinder were measured with the help of inclined multi-manometers. The wind velocity was kept constant at 13.5 m/s. The pressure coefficients were calculated from the measured values of the surface static pressure distribution on the cylinder. Later the drag and lift coefficients were obtained from the pressure coefficients by the numerical integration method. The results will enable the engineers and architects to design buildings more efficiently. Since the results will be expressed in the nondimensional form they may be applied for the prototype building. DOI: http://dx.doi.org/10.3329/jme.v44i1.19499

The main objective of the paper is to find the probable causes behind the shifting course of the Haora River, one of the major rivers of West Tripura and detachment of one of its major tributaries, the Katakhal River. From a recent satellite image, we observed that the River Haora has changed its course drastically near the confluence. Earlier, it used to take a sharp northward bend to meet with the River Titas immediately after crossing the Indo-Bangladesh border; but presently it is flowing westward to do so. Moreover, the Katakhal River, a right bank tributary of the River Haora, that used to flow through the northern side of the city of Agartala and meet with the River Haora at Bangladesh, is no longer a tributary of the Haora River. Now it is completely detached from the Haora River and meets with the River Titas separately. Spatiotemporal maps have been used to detect the changes. Field investigation, with the help of GPS, has been done in order to find the link between the Haora River and the Katakhal River within the Indian territory. Changing patterns of the Haora and Katakhal River confluences are also analysed, and earlier courses are identified. The shifting trends of both of these two rivers are found along the flanks of the interfluvial area because of microscale tectonic activity, i.e., upliftment of the interfluvial zone.

Soil erosion is one of the most important environmental problems, and it remains as a major threat to the land use of hilly regions of Tripura. The present study aims at estimating potential and actual soil loss (t·h-1·y-1) as well as to indentify the major erosion prone sub-watersheds in the study area. Average annual soil loss has been estimated by multiplying five parameters, i.e.: R (the rainfall erosivity factor), K (the soil erodibility factor), LS (the topographic factor), C (the crop management factor) and P (the conservation support practice). Such estimation is based on the principles de- fined in the Universal Soil Loss Equation (USLE) with some modifications. This intensity of soil erosion has been divided into different priority classes. The whole study area has been subdivided into 23 sub watersheds in order to identify the priority areas in terms of the intensity of soil erosion. Each sub-watershed has further been studied intensively in terms of rainfall, soil type, slope, land use/land cover and soil erosion to determine the dominant factor leading to higher erosion. The average annual predicted soil loss ranges between 11 and 836 t·h-1·y-1. Low soil loss areas (·h-1·y-1) have mostly been recorded under densely forested areas.

The landslide susceptibility map delineates the potential areas of landslide occurrence which is considered to be the first step for landslide hazard management. The present study focuses on the spatial analysis of landslide susceptibility in the Dhalai district using the Geographical Information System (GIS). For this purpose, landslide susceptibility maps are prepared using weight-rating and Analytical Hierarchical Processes (AHP). To analyze landslide manifestation in the present study area, different causative factors (lithology, road buffer, slope, relative relief, rainfall, fault buffer, land-use/land-cover, and drainage density) are derived as layers. The final susceptibility zonation map of weight-rating method shows that about 1.64 and 16.68 % of the total study area falls under very high and high susceptibility zones respectively. In the AHP method, the five landslide susceptibility zones are very low which accounted 14.8 % (354.35 km2) is, low 38.91 % (932.01 km2), moderate 34.75 % (832.37 km2), high 6.03 % (144.39 km2), and very high 5.51 % (131.87 km2). Both susceptibility maps show that the high susceptibility zone is restricted within the structural hilly areas and the low susceptibility zone is in the flood plain areas of the district. Both of the susceptibility maps are validated using the existing landslide distribution in the area.

With the rapid growth of population, design and construction of taller buildings are being emphasized now-a-days. Especially the design of the group of tall buildings is economic to take care of the housing problem of the huge population. As buildings become taller, effect of wind on them also increases. In this research work, experiments have been conducted to investigate the wind effect on a combination of pentagonal and hexagonal cylinders. The test was conducted in an open circuit wind tunnel at a Reynolds number of Re = 4.22 × 104 based on the face width of the cylinder across the flow direction in a uniform flow velocity of 13.5 m/s. A pentagonal cylinder was placed in the upstream and another two hexagonal cylinders were in the downstream. The transverse and longitudinal spacing between the cylinders were varied and the surface static pressures at the different locations of the cylinders were measured with the help of inclined multi-manometers. From the measured values of surface static pressures, ...

In this research work, an experimental investigation of wind effect on pentagonal and hexagonal staggered cylinders was carried out. The study was performed on the group consisting of three cylinders, arranged in staggered form, one pentagonal cylinder in the upstream and another two hexagonal cylinder in the downstream side. The test was conducted in an open circuit wind tunnel at a Reynolds number of 4.22 x 10 4 based on the face width of the cylinder across the flow direction in a uniform flow velocity of 13.5 m/s. The group of three cylinders was taken into consideration for the study and the surface static pressures were measured for various transverse spacing of 2D, 3D, 5D and longitudinal spacing of 1D, 2D, 4D, 6D, 8D, where D is the width of the cylinder across the flow direction. The surface static pressures at the different locations of the cylinder were measured with the help of inclined multi-manometers. The pressure coefficients were calculated from the measured values of the surface static pressure distribution on the cylinder. Later the drag and lift coefficients were obtained from the pressure coefficients by the numerical integration method. The results will enable the engineers and architects to design buildings more efficiently. Since the results will be expressed in the non-dimensional form they may be applied for the prototype building.