Late quaternary fluvial incision and aggradation in the Lesser Himalaya, India
Anthony DossetoJan‐Hendrik MayJeong‐Heon ChoiZachary J. SwanderDavid FinkOliver KorupPaul HesseTejpal SinghCharles MifsudPradeep Srivastava
8
Citation
52
Reference
10
Related Paper
Citation Trend
Keywords:
Aggradation
Bedrock
Stream power
Abstract Most bedrock river channels have a relatively thin, discontinuous cover of alluvium and are thus termed mixed bedrock‐alluvial channels. Such channels often show a series of steps formed at relatively regular intervals. This bed form is the bedrock equivalent of cyclic steps formed on beds composed of cohesive soil in gullies. In this paper, we perform a full nonlinear analysis for the case of cyclic steps in mixed bedrock‐alluvial channels to explain the formation of these steps. We employ the shallow water equations in conjunction with equations describing the process of bedrock incision. As a model of bedrock incision, we employ the recently introduced Macro‐Roughness Saltation Abrasion Alluviation model, which allows direct interaction between alluvial and bedrock morphodynamics. The analysis is greatly simplified by making the quasi‐steady assumption that alluvial processes occur much faster than bedrock erosional processes. From our analysis, we obtain the conditions for the formation of cyclic steps in bedrock, as well as the longitudinal profiles of bed elevation, water surface elevation, and areal fraction of alluvial cover. It is found from the analysis that when the sediment supply is small relative to the transport capacity, cyclic steps form only on slopes with very high gradients. The analysis indicates that the shape of a step formed on bedrock is characterized by a relatively short upstream portion with an adverse slope and a long, almost planar downstream portion with a constant slope.
Bedrock
Cite
Citations (30)
Tufas are constructional landforms composed of calcium carbonate. They are common in karst terrains, and are known worldwide as useful archives of palaeoenvironmental information. In the case of fluvial tufas, these carbonate deposits experience net aggradation when environmental conditions are stable, whilst incision through the deposits occurs when conditions become wetter. In this study, the first of its type in temperate Australia, we used geomorphological and sedimentological evidence preserved in fossil tufas and alluvial terraces to investigate the fluvial history of Davys Creek (NSW, Australia). The nature and timing of fluvial changes along two quasi-independent reaches of the creek were synchronous, suggesting the operation of externally driven processes rather than local internal fluvial adjustments. Following a period of sustained aggradation, rapid incision occurred along the creek between 1500 and 1600 years before present ( bp ) in response to a shift to a moister climate. This was succeeded by a second major aggradation event (1500 years bp to 150 years bp ), then subsequent incision following the arrival of Europeans at 150 years bp.
Aggradation
Tufa
Landform
Cite
Citations (7)
On the basis of the observation data of strip mining under structure and combining with numerical simulation,the surface subsidence rule of different mining and reservation width in strip mining under thick alluvium and thin bedrock were analyzed.The study shows that the calculated subsidence coefficient according to common strip mining is smaller than the actual value;the subsidence increases along with bedrock thinning with same mining width,and it is small when mining width is small with same bedrock;the subsidence increases more obviously with mining width increasing with thinner bedrock.In order to ensure the significance to control subsidence,while designing the mining and reservation width,not only design principle but also bedrock thickness should be considered,which can make the supporting terrane exist in bedrock.
Bedrock
Alluvion
Cite
Citations (2)
Glacial landscape forms are inherited by rivers following deglaciation. Hillslopes and valley floors configured by glacial erosion control the distribution of bedrock channels and potential sites for fluvial incision. The importance of ‘stream power’ parameters, channel slope and drainage area (discharge), in controlling the rate of incision is widely accepted, but the rate, timing and mechanisms of incision have yet to be quantified in these settings. The dual controls of glacially conditioned bedrock slopes and sediment supply set two of the key boundary conditions for temporally and spatially dynamic fluvial bedrock incision. Measurement of incision rates in these settings is key to understanding the influence of controls on fluvial erosion, and the role of the process in long-term evolution of deglaciated landscapes. In tectonically-passive, hard-rock terrains, such as the Scottish Highlands, incisional fluvial features such as bedrock channels, gorges and waterfalls are common on glacially carved valley steps. Here we report preliminary data on fluvial incision rates measured with cosmogenic 10Be. Our results confirm a postglacial age of bedrock straths in the NW Scottish Highlands and indicate a vertical incision rate of 0.3 mm/yr into resistant quartzites. Further work will explore erosion mechanisms and rates of incision across the Scottish Highlands, and assess controls on fluvial incision, including the potential role of paraglacial sediment.
Bedrock
Deglaciation
Cite
Citations (0)
The fluvial process of establishing new equilibrium in river section upstream of Aojiang River estuary due to constructed reservoir is studied by means of 1-D tidal flow-sediment mathematical model coupling with 2-D model.The characteristics of hydrology,sediment transport and fluvial process are analyzed.The calculation condition, the techniques for solving some key problems and verification of computation results are presented.The flow and fluvial process are predicted.It is found that the aggradation develops rapidly in the early stage after construction of reservoirs and it tends to degrade afterward until a new equilibrium is established.The aggradation process develops from upstream to downstream and the thickness of deposition at the river bend is smaller than the transition section between two bends.The water depth of navigation at the port will be affected by the sediment deposition.
Aggradation
Deposition
River regime
Cite
Citations (2)
Shallow seismic‐reflection techniques were used to image the bedrock‐alluvial interface, near a chemical evaporation pond in the Texas Panhandle, allowing optimum placement of water‐quality monitor wells. The seismic data showed bedrock valleys as shallow as 4 m and accurate to within 1 m horizontally and vertically. The normal‐moveout velocity within the near‐surface alluvium varies from 225 m/s to 400 m/s. All monitor‐well borings near the evaporation pond penetrated unsaturated alluvial material. On most of the data, the wavelet reflected from the bedrock‐alluvium interface has a dominant frequency of around 170 Hz. Low‐cut filtering at 24 dB/octave below 220 Hz prior to analog‐to‐digital conversion enhanced the amplitude of the desired bedrock reflection relative to the amplitude of the unwanted ground roll. The final bedrock contour map derived from drilling and seismic‐reflection data possesses improved resolution and shows a bedrock valley not interpretable from drill data alone.
Bedrock
Reflection
Cite
Citations (89)
Abstract To better understand how stream geomorphology may affect water temperature, we recorded water temperatures along two channels, one with deep alluvium and the other composed of bedrock and shallow alluvium. Study channels were located in managed forestlands on the Olympic Peninsula. Water temperatures were recorded hourly at 75-m intervals along 1.6 and 1.4 km of the alluvial and bedrock channels, respectively, during the summers of 2003 and 2004. Seasonal maximum and minimum daily water temperatures (i.e., season-long means for individual temperature dataloggers) in the alluvial channel tended to vary less over the course of the summer than temperatures in the bedrock channel. In addition, the means of all the individual dataloggers' daily maximums for each stream (reach mean maximum) and, similarly, the daily minimums (reach mean minimum) varied less for the alluvial channel. Changes in temperature from the upstream to downstream were greater for the bedrock channel, but only at low flow.
Bedrock
Peninsula
Alluvial fan
Alluvial soils
Cite
Citations (3)
Modeling of the annual heat flow within a thin alluvium veneer on a granitic bedrock substrate in desert environments, such as found in the southwestern United States, predicts that at certain times of the year the depth to bedrock has a measurable effect on the surface temperature if the alluvium cover is less than 2 m thick. Changes in the thickness of the alluvial cover caused by bedrock topography will produce contrasts in the surface temperature. If temperature contrasts as small as 0.1 C can be resolved, a linear topographic feature having several metres of relief buried by 1.5 m of alluvium may be visible in thermal imagery acquired during January or August in the southwestern U.S. under optimal conditions. Thermal remote sensing may provide a means for delineating some buried faults, fluvial channels, and other features of interest on buried, granitic pediment surfaces.
Bedrock
Alluvion
Alluvial fan
Cite
Citations (5)
Bedrock, resistant alluvium and gravel armor constrain channel behavior and morphology (Figure 1.2). Rivers that are confined between bedrock canyon walls are obviously dominated by bedrock. However, many rivers are only partly affected by bedrock, and they vary greatly in their morphology and ability to adjust in a downstream direction. For example, the Snake River in Idaho (Osterkamp et al., 2001), the Middle Fork of the John Day River in Oregon (McDowell, 2001), and the Sabie River in South Africa (Heritage et al., 2001) are of this type. Mapping of 25 km of the Sabie River reveals that 5 km is bedrock anastomosing, 6.5 km is pool-rapid, 8 km is mixed bedrock and alluvial anastomosing, 1 km is single thread, and 4.5 km is braided, a very mixed bag.
Bedrock
Alluvion
Cite
Citations (0)
ABSTRACT The nature and timing of fluvial response and coincident changes in climate as inferred from multiple, independent proxies are examined in the wet tropics of north‐eastern Australia. Chronostratigraphic data provide evidence for regionally synchronous fluvial aggradation at 30–13 ka, 8–5 ka and again from 1 ka. Terrace incision and removal occurred at 13–8 ka and 5–1 ka. A new synthesis of regional palaeoenvironmental proxy records spanning the last 30 ka highlights key periods of environmental change. Comparison of the records of fluvial and environmental change reveals the relationship is complex with no clear relationship between river aggradation/incision and wetter/drier conditions. The nature and timing of fluvial response in the wet tropics also shows broad similarities with coastal valleys in south‐eastern New South Wales, suggesting continental‐scale controls on fluvial response to changing climate during the Late Quaternary in Australia. Copyright © 2017 John Wiley & Sons, Ltd.
Aggradation
Paleoclimatology
Cite
Citations (15)