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Modelling the hydrological effects of land-use change in small catchmentSon, Ill January 1990 (has links)
No description available.
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Long and short term channel change in gravel bed riversThompson, A. January 1984 (has links)
No description available.
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Monitoring and modelling morphology, flow and sediment transport in a gravel-bed streamLane, Stuart Nicholas January 1994 (has links)
No description available.
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Downstream trends of alluvial sediment composition and channel adjustment in the Llano River watershed, Central Texas, USA : the roles of a highly variable flow regime and a complex lithologyHeitmuller, Franklin Thomas 05 February 2010 (has links)
This study investigates the downstream controls of alluvial sediment
composition and river channel adjustment in the Llano River watershed, Central Texas,
USA. The Llano River watershed is characterized by a highly variable, flood-prone
flow regime and a complex lithology of Cretaceous carbonate rock, Paleozoic
sedimentary rock, and Precambrian igneous and metamorphic rock. Sedimentary
variables for this study include particle size, sorting, carbonate content, and magnetic
susceptibility. Channel adjustment includes the planform dimension and cross-sectional
dimensions of bankfull- and macro-channels. Nineteen sites along the Llano River and
selected tributaries were visited to measure cross-sectional channel geometry and
sample bed, bank, and overbank sediment. Laboratory analyses of sediment and
hydraulic analyses of cross sections were accompanied by analyses of partial-duration
flood frequency, flow resistance, hydrography, digital elevation models, and statistical correlation. Findings include: (1) channel-bed material reduces in size with downstream
distance, despite increasing valley confinement and bedrock exposure; (2) the
downstream decrease in particle size is more evident for channel-bar deposits than for
low-flow-channel (thalweg) deposits; (3) an abrupt gravel-to-sand transition occurs
about 20 kilometers downstream of the Paleozoic-Precambrian contact; (4) an abrupt
coarse- to fine-gravel transition occurs between 75 and 90 kilometers downstream the
North Llano and South Llano Rivers; (5) channel-bank material increases downstream,
contrasting with decreases in bed material; (6) carbonate content and magnetic
susceptibility of alluvial sediment are inversely related, with carbonate content peaking
near Junction; (7) four general categories to classify reaches of the North Llano, South
Llano, and Llano Rivers are based on hydrology, planform morphology, lithology, and
valley confinement; (8) mean depth increasingly compensates for bankfull discharge in
a downstream direction; (9) mean depth compensates more than width for macrochannels;
and (10) the return periods for bankfull and macro-channels are about 1 to 2
years and greater than 10 years, respectively. The results of this study will contribute to
fluvial geomorphic theory of downstream trends in sediment composition and channel
adjustment; as well as inform applied efforts related to aquatic biology, flood hazards,
infrastructure design, and riparian and water-resource management in the region. / text
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Sediment transport dynamics in the lower Mississippi River : non-uniform flow and its effects on river-channel morphologyNittrouer, Jeffrey Albert 24 January 2011 (has links)
This dissertation examines the dynamics of sediment transport and channel morphology in the lower Mississippi River. The area of research includes the portion of the river where reach-averaged downstream flow velocity responds to the boundary condition imposed by the relatively uniform water-surface elevation of the receiving basin. Observational studies provided data that are used to identify channel-bed sediment composition, and measure bed-material sediment flux and the properties of the fluid-flow field over a variety of water-discharge conditions. The analyses demonstrate that a significant portion of the channel bed of the final 165 kilometers of the Mississippi River consists of exposed and eroding underlying relict sedimentary strata that qualify as surrogate bedrock. The exposed bedrock is confined to the channel thalweg, particularly in river-bend segments, and actively mobile bed-material sediments are positioned on subaqueous bars fixed by river planform. The analyses for sediment flux provides insight to the nature of sediment transport: during low- and moderate-water discharge, bed-material movement occurs primarily as minimal bedform flux, and so bed materials are not transferred between alluvial bars. During high-water discharge, bed-material transport increases one-hundred fold, and sands move as a part of both suspended and bedform transport. Physical models are used to show that skin-friction shear stress increases by a factor of ten for the measured water-discharge range. This change is not possible given conditions of uniform water flow, and therefore non-uniform flow in response to the Mississippi River approaching its outlet has a significant impact on the timing and magnitude of sediment flux through the lower river. In order to estimate the dynamics of bed material movement from the uniform to non-uniform segment of the river (lower 800 km), data for channel morphology are used to construct a model that predicts spatial changes in water-flow velocity and bed-material flux over a range of water-discharge conditions. The model demonstrates that non-uniform flow tends to produce a region of net channel-bed aggradation between 200-700 kilometers above the outlet, and a region of channel-bed degradation for the final 200. The implication for these results for the spatial variability of channel morphology and kinematics is explored. / text
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Mechanisms of Vegetation-Induced Channel Narrowing on an Unregulated Canyon-Bound RiverManners, Rebecca Blanche 01 August 2013 (has links)
The processes and interactions that determine the width of a river channel remain a fundamental area of investigation in geomorphology. An increasing appreciation of the capacity of riparian vegetation to alter fluvial processes, and thus influence channel form, has highlighted the need to include vegetation in these analyses. However, a disconnect exists between the small spatial and temporal scales over which the linkages among flow patterns, sediment, and plants are evaluated and the larger spatial and temporal scales in which river systems operate. In this dissertation, I strove to identify some of the key mechanisms by which vegetation affects channel width. I worked to reconcile the issue of scale by developing a novel tool that resolves patch-scale (sub-meter) patterns of hydraulic roughness over the reach scale. While the approach can be generalized to evaluate any vegetated floodplain, the multi-scalar model was specifically applied to stands dominated by the non-native riparian shrub, tamarisk, that invaded the riparian corridor of southwestern US rivers during the past century. I focused my analyses on the lower Yampa River in western Colorado. Tamarisk colonized the Yampa in the absence of other environmental perturbations. As a result, adjustments to channel form may be linked to an altered vegetation community. From a careful geomorphic and vegetation reconstruction of the Yampa, I determined that tamarisk was the driving force in channel narrowing. Application of the multi-scalar model of vegetation resistance to the Yampa enabled me to reconstruct the changing hydraulic conditions as tamarisk established and the channel narrowed over time. This hydraulic reconstruction furthered our understanding of the interactions among vegetation recruitment patterns, the increased hydraulic resistance, and the changing flow and sediment transport field. Positive feedbacks between vegetation and geomorphic change created additional areas within the channel where tamarisk could establish, and thus accelerated the rate of channel narrowing. However, these feedbacks also changed the importance of common and large floods for vegetation establishment and sediment transport. Application of this process-based understanding to future flow regimes will help managers anticipate locations along the channel that are susceptible to vegetation encroachment and changes to channel width.
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Derivation of Coastal Bathymetry and Stream Habitat Attributes Using Remote Sensing Images and Airborne LiDARSu, Haibin 26 September 2011 (has links)
No description available.
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ENABLING LARGE-SCALE HYDROLOGIC AND HYDRAULIC MODELING THROUGH IMPROVED TOPOGRAPHIC REPRESENTATIONSayan Dey (7444328) 19 December 2021 (has links)
<p>Topography is one of the primary drivers of
physical processes in the rivers and floodplains. Advances in remote-sensing
and survey techniques have provided high-resolution representation of the
floodplains but information regarding the 3D representation of river channels
(commonly known as river bathymetry) is sparsely available. Field surveys along
an entire river network in a watershed remains infeasible and algorithms for
estimating simple but effective characterization of river channel geometry are
hindered by an incomplete understanding of the role of river bathymetry in
surface and subsurface processes. </p>
<p> The
first objective of this dissertation develops an automated framework – System
for Producing RIver Network Geometry (SPRING) for improving the geospatial
descriptors of a river network. The tool takes as input the DEM and erroneous
river centerline to produce spatially consistent river centerlines, banks, and
an improved representation of river channel geometry. SPRING can process entire
river networks and is not limited single reach applications. The proposed
framework is flexible in terms of data requirements, resolution of output
datasets and user preferences. It has a user-friendly graphic user interface
(GUI) and is appropriate for large-scale applications since it requires minimal
user input.</p>
<p> A
better understanding of the role of bathymetric characteristics in surface-subsurface hydrology and hydrodynamics can
facilitate an efficient incorporation of river bathymetry in large river
networks. The second objective explores the level of bathymetric detail
required for accurately simulating surface and subsurface processes by developing
four bathymetric representations using SPRING with reducing level of detail.
These bathymetric configurations are simulated using a physically based tightly
coupled hydrologic and hydrodynamic model to estimate surface and subsurface
fluxes in the floodplains. Comparison of fluxes for the four bathymetric
configurations show that the impact of river bathymetry extends beyond surface
routing to surface water – groundwater interactions. Channel conveyance
capacity and thalweg elevation are the most important characteristics
controlling these interactions followed by channel side slope and channel
asymmetry. </p>
<p> The
final objective aims to develop benchmarks for bathymetric characteristics for
accurately simulating flooding related physical processes. The sensitivity of
surface and subsurface fluxes to error in channel conveyance capacity is
investigated across reaches with varying geomorphological characteristics. SPRING
is used to create six bathymetric configurations with varying range of error in
channel conveyance capacity (ranging from 25% to 300%). They are simulated
using a tightly coupled physically distributed model for a flood event and the
estimates of water surface elevation, infiltration and lateral seepage are compared.
Results show that incorporating channel conveyance capacity with an error of
within 25% significantly improves the estimates of surface and subsurface
fluxes as compared to those not having any bathymetric correction. For certain
reaches, such as those with high drainage area (>1000km<sup>2</sup>) or low
sinuosity (< 1.25), errors of up to 100% in channel conveyance capacity can still
improve H&H modeling.</p>
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Posouzení možnosti revitalizace vodního toku Osoblaha – úsek I / Assessment of the Possibilities The Revitalization of a Watercourse Osoblaha – Reach IMitana, Petr January 2015 (has links)
Diploma thesis deal with the issue revitalization of water stream. Assessment and design of revitalization is done for watercourse Osoblaha, situated in the cadastral territory Osoblaha nad Studnice by Osoblaha. In diploma thesis were designed several of revitalization measures such as stone backfill, willow fence, groyne, casting willow cuttings to supplement the vegetation on river‘s banks, fish shelter and wirestone baskets (gabions). In the given section was designed pool and also was there designed boulder slip, which will replace present downflow step. After designing was made hydrotechnical calculations to demostrate preservation runoff conditions of present stream condition.
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Návrh pohyblivého jezu na řece Želivce / Design of gated weir on the Želivka riverStaněk, Tomáš Unknown Date (has links)
The purpose of the diploma thesis „Design of a movable weir on the Želivka river" is a design of the reconstruction of a fixed weir in Soutice village on the river Želivka at km 1,639. The first part of the thesis deals with the localization of the area of interest and a description of all documents needed for the weir design. The first part also includes a short search of the considered structures, the findings of which are further applied in the design of a movable weir structure. Furthermore, the work continues by determining the design flow and selecting a suitable structure of the fixed weir substructure and movable closure, which is fitted to the substructure. Based on the selected types of structures, hydrotechnical calculations are performed, which also include a partial assessment of the weir stability. The thesis ends with a technical description of the proposed objects and a final evaluation of the determined achievements of the work. Part of the study is a drawing part documenting designed objects.
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