Arc River: Geo-Referenced Representation of River Hydrodymnamics

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Modelling the Eddy Pattern in the harbour of Zeebrugge

Hydrodynamic

Field-based measurement of hydrodynamics associated with engineered in-channel structures: the example of fish pass assessment

The construction of fish passes has been a longstanding measure to improve river ecosystem status by ensuring the passability of weirs, dams and other in- channel structures for migratory fish. Many fish passes have a low biological effectiveness because of unsuitable hydrodynamic conditions hindering fish to rapidly detect the pass entrance. There has been a need for techniques to quantify the hydrodynamics surrounding fish pass entrances in order to identify those passes that require enhancement and to improve the design of new passes. This PhD thesis presents the development of a methodology for the rapid, spatially continuous quantification of near-pass hydrodynamics in the field. The methodology involves moving-vessel Acoustic Doppler Current Profiler (ADCP) measurements in order to quantify the 3-dimensional water velocity distribution around fish pass entrances. The approach presented in this thesis is novel because it integrates a set of techniques to make ADCP data robust against errors associated with the environmental conditions near engineered in-channel structures. These techniques provide solutions to (i) ADCP compass errors from magnetic interference, (ii) bias in water velocity data caused by spatial flow heterogeneity, (iii) the accurate ADCP positioning in locales with constrained line of sight to navigation satellites, and (iv) the accurate and cost-effective sensor deployment following pre-defined sampling strategies. The effectiveness and transferability of the methodology were evaluated at three fish pass sites covering conditions of low, medium and high discharge. The methodology outputs enabled a detailed quantitative characterisation of the fish pass attraction flow and its interaction with other hydrodynamic features. The outputs are suitable to formulate novel indicators of hydrodynamic fish pass attractiveness and they revealed the need to refine traditional fish pass design guidelines

Hydrodynamic modeling of tidal-fluvial flows in a large river estuary

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordThe transition between riverine and estuarine environments is characterised by a change from unidirectional to bidirectional flows, in a region referred to herein as the Tidally-Influenced Fluvial Zone (TIFZ). In order to improve our understanding of the hydrodynamics and morphodynamics of this zone, we present a combined field and numerical modelling study of the Columbia River Estuary (CRE), USA, tidally-influenced fluvial zone. The CRE is large measuring 40 km in length and between 5 and 10 km wide. A shallow water model (Delft3D) was applied in both 2D and 3D configurations and model sensitivity to the key process parameterizations was investigated. Our results indicate that a 2D model constrained within the estuary can sufficiently reproduce depth-averaged flow within the TIFZ of a stratified estuary. Model results highlight the interactions between tidal-, fluvial- and topographic-forcing that result in depth dependent tidal rectification, and thus zones of residual sediment transport that: i) may be flood-directed along shallow channel margins and in the lee of bars, and simultaneously ii) is ebb-directed within deeper channel thalwegs. This condition is enhanced at lower discharges, but increased fluvial discharge reduces the number and size of regions with net flood-directed sediment transport and flow. These sediment transport patterns provide a mechanism to extend the bar/island topography downstream, and generate flood-directed, ebb-directed, and symmetrical bedforms, all within the same channel. Analysis of the model data reveals flood-directed sediment transport is due to both tidal variability and mean flow. These results highlight the need to include the mean flow component (M0) when considering the long-term morphodynamic evolution in a TIFZ. Model results highlight the interactions between tidal-, fluvial- and topographic-forcing that result in depth dependent tidal rectification, and thus zones of residual sediment transport that: i) may be flood-directed along shallow channel margins and in the lee of bars, and simultaneously ii) is ebb-directed within deeper channel thalwegs. This condition is enhanced at lower discharges, but increased fluvial discharge reduces the number and size of regions with net flood-directed sediment transport and flow. These sediment transport patterns provide a mechanism to extend the bar/island topography downstream, and generate flood-directed, ebb-directed, and symmetrical bedforms, all within the same channel. Analysis of the model data reveals flood-directed sediment transport is due to both tidal variability and mean flow. These results highlight the need to include the mean flow component (M0) when considering the long-term morphodynamic evolution in a TIFZ

EFFECTS OF METEOROLOGIC EVENTS ON WAVE CLIMATE AND CURRENT REGIME IN A SHALLOW, MICROTIDAL BAY

Along coastal Louisiana and within the shallow microtidal Barataria Bay estuary, meteorological events can play a primary role in influencing wave climate and circulation patterns. Understanding the effects of hurricanes and smaller tropical storms on hydrodynamic processes is important for constraining and predicting hydrodynamic variation in Barataria Bay, which, largely due to impacts from wave energy, is currently experiencing rapid wetland loss and is a major focus of coastal restoration efforts. Two bottom-mounted upward-facing Acoustic Current Doppler Profilers and wave, temperature, and depth recorders were installed in the lower portions of Barataria Bay to measure the wave climate and three-dimensional current velocities. These data were used to constrain wave action and current velocity responding to the passage of meteorological events in the fall of 2020 and summer of 2021. Fetch distance, water depth, and local wind speed were used as variables in a linear wave theory model that predicts significant wave height. Model results indicate that variation in fetch contributes relatively more to the overprediction of wave heights during storms compared to depth variation, which results in nearly negligible impacts on wave height prediction within Barataria Bay. In the quiescent periods between events, wave heights and propagation directions were much less predictable, as wind direction had a wider range and magnitude decreased substantially. Analyses of depth-averaged velocities suggests diurnal constituents dominate periodicity. Storms that made landfall to the west of the bay resulted in enhanced subtidal current magnitude during pre-and post-landfall periods while the recorded storm that made landfall to the east of the bay showed much less subtidal current response. The results shed light on the impacts of extreme events on circulation and wave climate in Barataria Bay, with implications for suspended sediment transport in a degradational coastal system

Hydraulic validation of two-dimensional simulations of braided river flow with spatially continuous aDcp data

Gravel‐bed braided rivers are characterized by shallow, branching flow across low relief, complex, and mobile bed topography. These conditions present a major challenge for the application of higher dimensional hydraulic models, the predictions of which are nevertheless vital to inform flood risk and ecosystem management. This paper demonstrates how high‐resolution topographic survey and hydraulic monitoring at a density commensurate with model discretization can be used to advance hydrodynamic simulations in braided rivers. Specifically, we detail applications of the shallow water model, Delft3d, to the Rees River, New Zealand, at two nested scales: a 300 m braid bar unit and a 2.5 km reach. In each case, terrestrial laser scanning was used to parameterize the topographic boundary condition at hitherto unprecedented resolution and accuracy. Dense observations of depth and velocity acquired from a mobile acoustic Doppler current profiler (aDcp), along with low‐altitude aerial photography, were then used to create a data‐rich framework for model calibration and testing at a range of discharges. Calibration focused on the estimation of spatially uniform roughness and horizontal eddy viscosity, νH, through comparison of predictions with distributed hydraulic data. Results revealed strong sensitivity to νH, which influenced cross‐channel velocity and localization of high shear zones. The high‐resolution bed topography partially accounts for form resistance, and the recovered roughness was found to scale by 1.2–1.4 D84 grain diameter. Model performance was good for a range of flows, with minimal bias and tight error distributions, suggesting that acceptable predictions can be achieved with spatially uniform roughness and νH.Field campaigns were primarily funded by NERC Grant NE/G005427/1 and NERC Geophysical Equipment Facility Loan 892 as well as NSERC and CFI (Canada) grants to Colin Rennie. Damia Vericat was supported by a Ramon y Cajal Fellowship (RYC‐2010‐06264) funded by the Spanish Ministry of Science and Innovation during the preparation of this manuscript. Numerical simulations were undertaken during a visit by Richard Williams to NIWA. This visit was funded by the British Hydrology Society and an Aberystwyth University Postgraduate Studentship. Murray Hicks and Richard Measures were funded by NIWA core funding under the Sustainable Water Allocation Programme

Hydrologic Modeling of Navasota River Subchannel Inundation

Anastomosing rivers are multichannel systems characterized by a definitive main channel and semi-permanent sub-channels that intertwine with the main channel in their planform. This semi-permanence of the sub-channels is largely associated with flows that have been recognized to be fed by overbank flows from the main channel. The Navasota river on the coastal plain of Texas is an anastomosing river with ephemeral anabranches dependent on main channel over bank flow. This study determines the river stage at which the main channel becomes laterally connected to anabranching channels by surface water. The chosen study site on the Navasota is located at Democrat Crossing road that is downstream of U.S. Geological Survey gaging station 08110800 at Democrat Crossing road.. The purpose of this work is tomonitorthe interactions of fourdownstream anabranches within a .5-kmradius. Lateral connections between the main channel and sub-channels are determined using a two-dimensional hydrodynamic model that was developed using a LiDAR-based digital terrain model and calibrated/validated using acoustic and topographic surveys conducted in the field. Preliminary analysis suggests there are 3 stages of connection, (1) exclusively the main channel, (2) lower level anabranch connections, and (3) upper level anabranch. The riverine landscape of the Navasota River shelters high levels of ecological diversity and surface water connections within a river reach can impact the overall health and evolution of these riverine ecosystem. This project provides a case study to promote knowledge of the flow dynamics of anastomosing geomorphology and water resource management applications within and upstream of the study site to help mitigate flooding hazards and help manage the riverine ecosystem

Proceedings of the XVIIIth Telemac & Mascaret User Club 2011, 19-21 October 2011, EDF R&D, Chatou

Water Qualit