Vegetation and landuse analysis of aglar watershed using satellite remote sensing technique

Wetershed management requires spatial knowledge of vegetation attribute, alongwith landuse, socio-economic and physical parameters. Aglar watershed, which drains in the river Yamuna, is situated in a socio-economically backward region. Any development plan in this region will require an approach which considers natural unit of watershed and its parameterisation. The study highlights the utility of space remote sensing data in obtaining spatial information of vegetation and existing landuse through visual interpretation of 1:50,000 scale Landsat TM false colour composite. Aglar watershed has been identified as forested having distinct vegetation distribution and landuse practice in southern and northern aspects of the watershed. Southern aspects are more inhabited and subjected to terrace cultivation and acute shortage of vegetation resources for fuelwood and fodder. The northern aspect is thickly vegetated with low-population density.     

Optimal Routefinding Across Landscapes Featuring High‐cost Linear Obstacles

Existing GIS‐based least‐cost routefinding approaches can in some cases be confounded by linear features in the landscape whose crossing costs are high relative to other traversing costs found throughout the landscape. Unfortunately, such high‐cost linear features are not uncommon; they frequently occur in the form of hydrologic features whose crossing costs are high relative to costs of traversing the surrounding dry land. This study (1) enumerates the situations where existing approaches can fail, (2) proposes a simple method for overcoming the limitations of the existing approaches, and (3) conducts an experiment to assess the impact of the weaknesses of existing approaches and the magnitude of the differences between the results produced by existing and revised approaches. Our results show that in mountainous terrain, linear hydrologic features with high crossing costs can have a profound impact on least‐cost routes, and the choice of solution method has equally profound impacts on the optimal route produced by the analysis.     

On the interaction of mesoscale eddies and a tropical cyclone in the Bay of Bengal

Natural Hazards - Oceanic eddies span over a wide range of sizes and affect the thermodynamic properties of water column. By modifying the thermal structure of the upper ocean, these eddies...     

Limnological Studies in a Subtropical System (Lake Sattal,India)

A limnological study was carried out in the subtropical Lake Sattal (Kumaun Himalaya) during 1979. The lake was thermally stratified during warm months and a low percentage saturation of dissolved oxygen occurred in the bottom waters. Two maxima of phytoplankton occurred in the Eastern basin in contrast to only one in the Western basin. The peak in the latter developed more than a month (October) after the second peak in the former (August). Bacillariophyceae contributed highest in the Western basin (43.2%) whereas the Dinophyceae had the least share in the Eastern basin (8.0%). Most of the dominant phytoplankters were: Synedra ulna, Fragilaria, Gymnodinium, Crucigenia and Closteridium siamensis. Interestingly, blue-green alga Nostoc, dominated for some time in autumn. A total of 12 genera of rotifers, 6 genera of cladocerans and 1 genus of copepods were found in Lake Sattal basins. Dominant zooplankters included Keratella, Cyclops, Anuraeopsis, Polyarthra and Trichocerca, and there is a high ratio of rotifers to copepods and cladocerans. On comparing the averaged values of both the basins, the Eastern basin showed a 64% larger population of zooplankton than the Western basin. A comparison is made with the plankton of the other subtropical lake-systems of this region.     

Physico-chemical Limnology of Lake Naini Tal,Kumaun, Himalaya (U. P.), India

The monomictic lake at a height of 1937 m, having an area of 48 ha, a mean depth of 16 m and a maximum depth of 27 m, is subjected to such an intensive use in its drainage area that the lake became eutrophicated. The spatial-temporal distribution of important physico-chemical criteria is represented for a period of two years. The depth of visibility varies between 0.4 m (March) and 2 m (June). The thermal stratification keeps up from March to November; therefore in the deep water zone a typical oxygen depletion and an enrichment of PO₄? P (26 μg/l) and of N_inerg (940 μg/l) occur. The pH-value lies in the alkaline range and shows a significantly positive correlation with primary production and temperature and a negative correlation with the carbonate content. Also the oxygen concentration is positively correlated with the primary production and temperature. During stagnation, the sediment/water contact zone is free of oxygen for ca. 70 % of the area.     

Relation between VLF phase deviations and solar X-ray fluxes during solar flares

Sudden phase anomalies (SPA's) observed in the phase of GBR 16 kHz VLF signals during the years 1977 to 1983 have been analysed in the light of their associated solar X-ray fluxes in the 0.5–4 Å and 1–8 Å bands. An attempt has been made to investigate the solar zenith angle () dependence of the integrated solar X-ray flux for producing SPA's. It is deduced from the observations for < 81° that the phase deviation increases linearly as a whole with increasing solar X-ray fluxes in these two bands. The threshold X-ray flux needed to produce a detectable SPA effect has been estimated to be 1.6 × 10^–4 ergcm^–2 s^–1 and 1.8 × 10^–3 ergcm^–2 s^–1 in the 0.5–4 Å and 1–8 Å bands, respectively. For both bands the average cross section for all atmospheric constituents at a height of 70 km is almost equal to the absorption cross section for the 3 Å X-ray emission.     

CODA Q estimates for Kumaun Himalaya

CodaQ (Q _c) estimates for the Kumaun Himalaya region have been obtained in high frequency range. Local earthquakes, recorded by a digital seismic network in the region, which fall in the epicentral distances range of 10 to 80 km and with a local magnitude range of 1.4 to 2.8, have been used. The coda waves of 30 sec window length, filtered at seven frequency bands centered at 1.5, 3, 6, 9, 12, 18 and 24Hz, have been analysed using the single backscattering model. The values ofQ _c estimates vary from 65 to 283 at 1.5 Hz to 2119 to 3279 at 24.0 Hz which showed thatQ _c is frequency dependent and its value increases as frequency increases. A frequency-dependentQ _c relationship,Q _c = (92 ± 4.73)f^(1.07±.023), is obtained for the region representing the average attenuation characteristics of seismic waves for Kumaun Himalaya region.     

Assessment of the dynamic response of unreinforced masonry structures using a macroelement modeling approach

The seismic performance of unreinforced masonry structures is strongly associated with the interaction between in‐plane and out‐of‐plane mechanisms. The seismic response of these structures has been thoroughly investigated by means of experimental testing, analytical procedures, and computational approaches. Within the framework of the numerical simulations, models based on the finite element method provide a good prediction of the seismic performance of unreinforced masonry structures. However, they usually require a high computational cost and advanced user expertise to define appropriate mechanical properties and to interpret the numerical results. Because of these limitations, simplified models for practical applications have been developed during the last decades. Despite this, a great number of these models focus mostly on the evaluation of the in‐plane response, assuming box (or integral) behavior of the structure. In this paper, a simplified macroelement modeling approach is used to simulate the seismic response of 2 masonry prototypes taking into consideration the combined in‐plane and out‐of‐plane action. The numerical investigations were performed in the static and dynamic fields by using pushover analyses and nonlinear dynamic analyses respectively. The latter is a novel implementation of a model previously developed for static analysis. The results obtained from this study are in good agreement with those provided by a detailed nonlinear continuum FE approach, demonstrating the applicability of this macroelement model with a significant reduction of the computational cost.