Factors controlling the morphology and volume (V)–length (L) relations of permanent gullies in the northern Ethiopian Highlands     

Amaury Frankl  Jean Poesen  Nelles Scholiers  Miró Jacob  Mitiku Haile  Jozef Deckers  Jan Nyssen 《地球表面变化过程与地形》2013,38(14):1672-1684

Small‐scale aerial photographs and high‐resolution satellite images, available for Ethiopia since the second half of the twentieth century as for most countries, allow only the length of gullies to be determined. Understanding the development of gully volumes therefore requires that empirical relations between gully volume (V) and length (L) are established in the field. So far, such V–L relations have been proposed for a limited number of gullies/environments and were especially developed for ephemeral gullies. In this study, V–L relations were established for permanent gullies in northern Ethiopia, having a total length of 152 km. In order to take the regional variability in environmental characteristics into account, factors that control gully cross‐sectional morphology were studied from 811 cross‐sections. This indicated that the lithology and the presence of check dams or low‐active channels were the most important controls of gully cross‐sectional shape and size. Cross‐sectional size could be fairly well predicted by their drainage area. The V–L relation for the complete dataset was V = 0 · 562 L ^1·381 (n = 33, r² = 0 · 94, with 34 · 9% of the network having check dams and/or being low‐active). Producing such relations for the different lithologies and percentages of the gully network having check dams and/or being low‐active allows historical gully development from historical remote sensing data to be assessed. In addition, gully volume was also related to its catchments area (A) and catchment slope gradient (S_c). This study demonstrates that V–L and V–A × S_c relations can be very suitable for planners to assess gully volume, but that the establishment of such relations is necessarily region‐specific. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Glacier changes using satellite data and effect of climate in Tirungkhad basin located in western Himalaya     

Riyaz Ahmad Mir  Sanjay K. Jain  Arun K. Saraf  Ajanta Goswami 《国际地球制图》2013,28(3):293-313

Glaciers are widely recognized as key indicators of climate change, and melt water obtained from them is an important source of fresh water and for hydropower generation. Regular monitoring of a large number of Himalayan glaciers is important for improving our knowledge of glacier response to climate change. In the present study, Survey of India topographical maps (1966) and Landsat datasets as ETM+ (2000, 2006) and TM (2011) have been used to study glacier fluctuations in Tirungkhad basin. A deglaciation of 26.1% (29.1?km²) in terms of area from 1966 to 2011 was observed. Lower altitude small glaciers (area?<?1?km²) lost more ice (34%), while glaciers with an area <10?km² lost less (20%). The percentage of change in glacier length was 26% (31.9?km) from 1966 to 2011. The south-facing glaciers showed high percentages of loss. From 2000 to 2011, debris cover has increased by 1.34%. The analysis of the trend in meteorological data collected from Kalpa and Purbani stations was carried out by Mann Kendall non-parametric method. During the last two decades, the mean annual temperature (T_max and T_min) has increased significantly, accompanied with a fall in snow water equivalent (SWE) and rainfall. The increasing trend in temperature and decreasing trend in SWE were significant at 95% confidence level. This observation shows that the warming of the climate is probably one of the major reasons for the glacier change in the basin.  相似文献   

Orbital period changes and photometric study of contact binary system AK Her     

A. Samadi  D.M.Z. Jassur  S. Nassiri  G. Gozaliasl  M.H. Kermani  A. Zareie 《New Astronomy》2010,15(4):339-342

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Photometric Study of Eclipsing Binary U Sagittae     

Davood Manzoori  Davood Mohammadzadeh Jassur  Mir Hojat Kermani 《Astrophysics and Space Science》2006,302(1-4):145-151

New UBV photometry of Algol type binary star U Sge obtained during 1993 are presented, analyzed, and discussed. Wilson-Devinney code was employed to analyze the light curves. Absolute dimensions of the system were obtained, and positions of both components on H-R diagram were specified. Finally through color curve analysis absolute visual magnitudes were determined.  相似文献   

An experimental investigation into earthquake-induced failure of medium to low height concrete gravity dams     

Riyaz A. Mir  C. A. Taylor 《地震工程与结构动力学》1995,24(3):373-393

A suitable model material was developed to construct scaled models of a 30 m high prototype concrete gravity dam monolith and the experimental technique perfected for testing the models, till failure, on the EPSRC earthquake simulator at Bristol University. A series of shaking table tests was performed with the aim of assessing the possible failure mechanisms of medium to low height dams under simple motions and simulated earthquakes. Tests were conducted with and without the presence of hydrostatic pressure. The hydrodynamic pressure was simulated using Westergaard's added mass approach. Base cracking was observed to be the main failure mechanism and a tendency of the models to slide and rock after the full crack development at the interface was also observed in some cases.  相似文献   

Concentrated flow erosion as a main source of sediments in Galicia,Spain     

José M. Mirás‐Avalos  Antonio Paz‐González  Jorge Dafonte‐Dafonte  Eva Vidal‐Vázquez  Montserrat Valcárcel‐Armesto 《地球表面变化过程与地形》2009,34(15):2087-2095

Knowledge of soil loss rates by water erosion under given climate, soil, topography, and management conditions is important for establishing soil conservation schemes. In Galicia, a region with Atlantic climatic conditions in Spain, field observations over the last decade indicate that interrill, rill and ephemeral gully erosion may be an important sediment source. The aim of this work was to assess concentrated erosion rates, describe types of rills and ephemeral gullies and determine their origin, evolution and importance as sediment sources. Soil surface state and concentrated flow erosion were surveyed on medium textured soils, developed over basic schists of the Ordenes Complex series (Coruña province, Spain) from 1997 to 2006. Soil surface state was characterized by crust development, tillage features and roughness degree. Soil erosion rate was directly measured in the field. Concentrated flow erosion took place mainly on seedbeds and recently tilled surfaces in late spring and by autumn or early winter. During the study period, erosion rates were highly variable and the following situations could be distinguished: (a) no incision or limited rill incision, i.e. below 2 Mg ha^?1 year^?1; (b) generalized rill and ephemeral gully incision in the class of mean values between 2·5 and 6·25 Mg ha^?1 year^?1, this was the most common erosion pattern; and (c) heavy erosion as observed during an extremely wet winter period, between October 2000 and February 2001, with erosion figures that may be about ten orders of magnitude higher, up to 55–60 Mg ha^?1 year^?1. Therefore, low values of soil losses are dominant, but also large values of rill and ephemeral gully erosion occurred during the study period. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Period changes and light curve analysis of eclipsing binary AB Andromedae     

A. Hasanzadeh  D. M. Z. Jassur  M. H. Kermani 《Astrophysics and Space Science》2008,317(1-2):71-77

BV photometry of close binary star AB And in two observational seasons have been presented. Updated O-C diagram analysis by Kalimeris method yielded the values of 0.0188 day and 0.0065 day as amplitudes of orbital period modulation with P _mod1～61 yr and P _mod2～34 yr as the modulation periodicities. Light curve analysis was carried out by W-D method and geometric and physical parameters of the components. Finally, the consequences of period changes have been discussed on the basis of light-time effect due to third body in the system and Applegate mechanism.  相似文献   

Detection of Changes in Glacier Mass Balance Using Satellite and Meteorological Data in Tirungkhad Basin Located in Western Himalaya     

Riyaz Ahmad Mir  Sanjay K. Jain  Arun K. Saraf  Ajanta Goswami 《Journal of the Indian Society of Remote Sensing》2014,42(1):91-105

Himalayan glaciers and their mass balance are poorly sampled through direct mass balance measurements. Thus, based on Landsat datasets of ETM⁺ (2000), ETM⁺ (2006) and TM (2011), mass balance studies of 32 glaciers was carried out using accumulation area ratio (AAR) method in the Tirungkhad river basin, a tributary of Satluj River, located in western Himalayan region. The overall specific mass balance was negative varying from ?27 cm (2000) to ?41 cm (2011). Out of 32 glaciers, 27 glaciers (81.2 %) showed negative mean mass balance and 5 glaciers (18.7 %) showed positive mean mass balance. Mean of specific mass balance for the year 2000, 2006 and 2011 was found to be ?48 cm, ?55 cm and ?0.61 cm respectively, in case of glaciers with negative mass balance while in case of glaciers with positive mass balance, it was 0.67 cm (2000), 0.56 cm (2006) and 0.47 cm (2011). The investigations suggested a loss of ?0.034 km³ of glacial ice for 2000, 0.036 km³ for 2006 and 0.038 km³ for 2011 respectively. The negative mass balance of the glaciers since 2000 correlates well with the increasing trend of annual mean temperature and decreasing trend of precipitation (snow water equivalent (SWE) and rainfall). Based on Mann Kendall test the temperature and SWE trends were significant at 95 % confidence level, however, the rainfall trend was insignificant.  相似文献   

Numerical study on static and seismic stability of breakwaters on soft granular marine deposits against deep failure     

Mehdi Veiskarami  Mir Ahmad Lashteh Neshaei  Mehran Karimpour Fard  Tina Pourramezan 《Marine Georesources & Geotechnology》2017,35(1):42-51

Marine structures which cover a wide range of offshore and onshore structures are often subjected to different external and internal forces against which a proper design should be performed. Among many, breakwaters constructed over a relatively loose agglomerate of granular soils are much prone to deep seated failure extended beneath the foundation. This type of failure has been given less attention in conventional design approaches. Stability analysis of such failures is the main subject of this research which includes both the static and the seismic stability of breakwaters over granular marine soils. As the subsoil strata in sea beds often comprise loose sand deposits, it is more convenient to assume a rather small angle of dilation, at least at failure, which certainly reduces the potential to resist geotechnical instabilities. The method of stress characteristics along with slight modifications to handle this issue has been used to assess the overall stability of breakwaters against deep seated failures. Investigations revealed that while even under static condition, there is certain potential of failure, under seismic condition, the risk is quite very high. A series of design charts are also developed presenting the factor of stability as a measure of safety against such failure.  相似文献   

Ground motion modelling in northwestern Himalaya using stochastic finite-fault method     

Mir  Ramees R.  Parvez  Imtiyaz A. 《Natural Hazards》2020,103(2):1989-2007

Natural Hazards - This study presents estimates of bedrock level peak ground motion at 2346 sites on a regular grid of 0.2°?×?0.2° in northwestern (NW) Himalaya from 543...  相似文献