Thresholds in the Transformation of Slopes and River Channels in the Darjeeling Himalaya, India

1990 ◽  
Vol 10 (4) ◽  
pp. 301 ◽  
Author(s):  
W. Froehlich ◽  
E. Gil ◽  
I. Kasza ◽  
L. Starkel
Keyword(s):  
River Channels ◽  
Darjeeling Himalaya

ASSESSMENT OF HYDROLOGICAL CHANGES IN THE ŠUŠVĖ RIVER

2015 ◽  
Author(s):  
Gražina ŽIBIENĖ ◽  
Alvydas ŽIBAS ◽  
Goda BLAŽAITYTĖ
Keyword(s):  
Hydrological Regime ◽  
Maximum Flow ◽  
Environmental Flow ◽  
Physical Structure ◽  
River Channels ◽  
Hydrologic Alteration ◽  
Water Conditions ◽  
Flow Components ◽  
The Impact ◽  
Large Floods

The construction of dams in rivers negatively affects ecosystems because dams violate the continuity of rivers, transform the biological and physical structure of the river channels, and the most importantly – alter the hydrological regime. The impact on the hydrology of the river can occur through reducing or increasing flows, altering seasonality of flows, changing the frequency, duration and timing of flow events, etc. In order to determine the extent of the mentioned changes, The Indicators of Hydrologic Alteration (IHA) software was used in this paper. The results showed that after the construction of Angiriai dam, such changes occurred in IHA Parameters group as: the water conditions of April month decreased by 31 %; 1-day, 3-days, 7-days and 30-days maximum flow decreased; the date of minimum flow occurred 21 days later; duration of high and low pulses and the frequency of low pulses decreased, but the frequency of high pulses increased, etc. The analysis of the Environmental Flow Components showed, that the essential differences were recorded in groups of the small and large floods, when, after the establishment of the Šušvė Reservoir, the large floods no longer took place and the probability of frequency of the small floods didn’t exceed 1 time per year.

Foliar Micro-Morphological Traits in some Members of Ericaceae from Darjeeling Himalaya

Pleione ◽  
2017 ◽  
Vol 11 (2) ◽  
pp. 341
Author(s):  
Debapriya Karmakar ◽  
S. Moktan ◽  
A. P. Das
Keyword(s):  
Morphological Traits ◽  
Darjeeling Himalaya

Engineering impacts on river channels in the River Rhine catchment

Erdkunde ◽  
2005 ◽  
Vol 59 (3/4) ◽  
pp. 294-319 ◽  
Author(s):  
Jürgen Herget ◽  
et al. et al.
Keyword(s):  
River Rhine ◽  
River Channels ◽  
Rhine Catchment

Boulders as a lithologic control on river and landscape response to tectonic forcing at the Mendocino triple junction

2020 ◽  
Author(s):  
Charles M. Shobe ◽  
Georgina L. Bennett ◽  
Gregory E. Tucker ◽  
Kevin Roback ◽  
Scott R. Miller ◽  
...  
Keyword(s):  
Triple Junction ◽  
High Elevation ◽  
River Channels ◽  
Erosion Rates ◽  
Coastal Belt ◽  
Sediment Mass ◽  
Mendocino Triple Junction ◽  
Landscape Response ◽  
Channel Steepness ◽  
Tectonic Forcing

Constraining Earth’s sediment mass balance over geologic time requires a quantitative understanding of how landscapes respond to transient tectonic perturbations. However, the mechanisms by which bedrock lithology governs landscape response remain poorly understood. Rock type influences the size of sediment delivered to river channels, which controls how efficiently rivers respond to tectonic forcing. The Mendocino triple junction region of northern California, USA, is one landscape in which large boulders, delivered by hillslope failures to channels, may alter the pace of landscape response to a pulse of rock uplift. Boulders frequently delivered by earthflows in one lithology, the Franciscan mélange, have been hypothesized to steepen channels and slow river response to rock uplift, helping to preserve high-elevation, low-relief topography. Channels in other units (the Coastal Belt and the Franciscan schist) may experience little or no erosion inhibition due to boulder delivery. Here we investigate spatial patterns in channel steepness, an indicator of erosion resistance, and how it varies between mélange and non-mélange channels. We then ask whether lithologically controlled boulder delivery to rivers is a possible cause of steepness variations. We find that mélange channels are steeper than Coastal Belt channels but not steeper than schist channels. Though channels in all units steepen with increasing proximity to mapped hillslope failures, absolute steepness values near failures are much higher (∼2×) in the mélange and schist than in Coastal Belt units. This could reflect reduced rock erodibility or increased erosion rates in the mélange and schist, or disproportionate steepening due to enhanced boulder delivery by hillslope failures in those units. To investigate the possible influence of lithology-dependent boulder delivery, we map boulders at failure toes in the three units. We find that boulder size, frequency, and concentration are greatest in mélange channels and that Coastal Belt channels have the lowest concentrations. Using our field data to parameterize a mathematical model for channel slope response to boulder delivery, we find that the modeled influence of boulders in the mélange could be strong enough to account for some observed differences in channel steepness between lithologies. At the landscape scale, we lack the data to fully disentangle boulder-induced steepening from that due to spatially varying erosion rates and in situ rock erodibility. However, our boulder mapping and modeling results suggest that lithology-dependent boulder delivery to channels could retard landscape adjustment to tectonic forcing in the mélange and potentially also in the schist. Boulder delivery may modulate landscape response to tectonics and help preserve high-elevation, low-relief topography at the Mendocino triple junction and elsewhere.

scholarly journals Sediment Transport and Water Flow Resistance in Alluvial River Channels: Modified Model of Transport of Non-Uniform Grain-Size Sediments

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2038
Author(s):  
Gennady Gladkov ◽  
Michał Habel ◽  
Zygmunt Babiński ◽  
Pakhom Belyakov
Keyword(s):  
Sediment Transport ◽  
Water Flow ◽  
Transport Model ◽  
Flow Characteristics ◽  
Field Measurements ◽  
Field Investigation ◽  
Empirical Modeling ◽  
River Channels ◽  
Channel Deformations ◽  
East European

The paper presents recommendations for using the results obtained in sediment transport simulation and modeling of channel deformations in rivers. This work relates to the issues of empirical modeling of the water flow characteristics in natural riverbeds with a movable bottom (alluvial channels) which are extremely complex. The study shows that in the simulation of sediment transport and calculation of channel deformations in the rivers, it is expedient to use the calculation dependences of Chézy’s coefficient for assessing the roughness of the bottom sediment mixture, or the dependences of the form based on the field investigation data. Three models are most commonly used and based on the original formulas of Meyer-Peter and Müller (1948), Einstein (1950) and van Rijn (1984). This work deals with assessing the hydraulic resistance of the channel and improving the river sediment transport model in a simulation of riverbed transformation on the basis of previous research to verify it based on 296 field measurements on the Central-East European lowland rivers. The performed test calculations show that the modified van Rijn formula gives the best results from all the considered variants.

Impacts of urbanization on river system structure: a case study on Qinhuai River Basin, Yangtze River Delta

2014 ◽  
Vol 70 (4) ◽  
pp. 671-677 ◽  
Author(s):  
Xiaomin Ji ◽  
Youpeng Xu ◽  
Longfei Han ◽  
Liu Yang
Keyword(s):  
River Basin ◽  
River System ◽  
Yangtze River Delta ◽  
System Structure ◽  
River Channels ◽  
Stream Structure ◽  
Impervious Area ◽  
The Status ◽  
Urbanized Areas ◽  
Qinhuai River

Stream structure is usually dominated by various human activities over a short term. An analysis of variation in stream structure from 1979 to 2009 in the Qinhuai River Basin, China, was performed based on remote sensing images and topographic maps by using ArcGIS. A series of river parameters derived from river geomorphology are listed to describe the status of river structure in the past and present. Results showed that urbanization caused a huge increase in the impervious area. The number of rivers in the study area has decreased and length of rivers has shortened. Over the 30 years, there was a 41.03% decrease in river length. Complexity and stability of streams have also changed and consequently the storage capacities of river channels in intensively urbanized areas are much lower than in moderately urbanized areas, indicating a greater risk of floods. Therefore, more attention should be paid to the urban disturbance to rivers.

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