Nils Rüther

Technische Universität München | TUM

The existing equations for the discharge coefficient of Piano key weirs (PKWs) use a limited range of experimental data, which means that they are inappropriate for wide parametric ranges that might lead to significant errors. This study aimed to propose a reformed empirical equation using a wide range of data points gathered from previous experime...

It is increasingly important to know the water quality of a reservoir, given the prospect of an environment poor in water reserves, which are based on intense and short-lived precipitation events. In this work, vegetation indices (NDVI, EVI) and bio-physical parameters of the vegetation (LAI, FC), meteorological variables, and hydrological data are...

In this study, the full Launder, Reece and Rodi pressure-strain model and nonlinear boundary damping functions were incorporated in OpenFOAM® to simulate the turbulence-driven secondary currents in supercritical narrow channel flows such as in sediment bypass tunnels (SBTs). Five simulations were performed under uniform flow conditions covering Fro...

The existing LRR Reynolds stress model in OpenFOAM uses the simplified rapid pressure strain model and linear wall damping function which previously produced weaker turbulence anisotropy and secondary currents. Therefore, the full LRR pressure strain model, the nonlinear wall & free surface damping functions, and the free surface boundary condition...

One of the most effective techniques to combat reservoir sedimentation, especially for small to medium-sized reservoirs, is the installation of Sediment Bypass Tunnels (SBTs). SBTs are designed for supercritical narrow open channel flow conditions. In such narrow channels, the walls and the free surface boundaries can influence the flow characteris...

The study reviews the two habitat models CASiMiR (microscale) and MesoHABSIM (mesoscale) regarding the aspects scale, data collection, model setup, handling habitat preferences, result presentation and application. Both models were applied at a river stretch at the upper Inn River in Austria, which provided a basis for closer comparison and analysi...

The river morphology of a braided type river is rather complex. High sediment transport rates and frequently changing discharges are the cause of dynamic planform evolution. The coexistence of alternating bars and the consequent appearing confluences and divergences in interaction with bank erosion have been in the focus of scientific investigation...

River confluences have a complex flow and sedimentation pattern that have vital influences on the hydraulic and bed morphology of river reach and the surrounding area. Confluences can be observed in waterways with various situations such as live bed conditions. This condition is a hydro-morphological situation with a high densimetric Froude number,...

Sedimentation is one of the main eco-morphological and technological challenges associated with reservoirs. Sedimentation not only reduces the functional capacity of a reservoir by filling it, but also changes downstream sediment dynamics and habitat availability for the aquatic biota. Additionally, dams hinder free bi-directional fish passage, eme...

Bedload transport is an important factor to describe the hydromorphological processes of fluvial systems. However, conven- tional bedload sampling methods have large uncertainty, making it harder to understand this notoriously complex phenom- enon. In this study, a novel, image-based approach, the Video-based Bedload Tracker (VBT), is implemented t...

The river flow and the sediment that composes the riverbed are in constant interaction. Despite its importance, this interaction still has undiscovered aspects and unanswered questions. In alluvial rivers, one important factor that describes their morphological changes is the bedload yield. Defining its value however, remains a complex task, where...

Secondary currents, turbulence characteristics and bed shear stress distribution are the crucial parameters for specifying sediment transport. Hence, to understand the sediment transport in sediment bypass tunnels (SBTs), we performed computational fluid dynamics (CFD) simulation of supercritical flow in a narrow straight channel. The results of th...

Flash floods can cause great geomorphological changes in ephemeral fluvial systems and result in particularly severe damages for the unprepared population exposed to it. The flash flood in the Storelva river in Utvik (western Norway) on 24 July 2017 was witnessed and documented. This study assessed the causes and effects of the 2017 flood and provi...

While designing physical hydraulic model tests to investigate the efficiency of pressure flushing, it is most likely that very fine sediments of cohesive nature are required to satisfy the relevant scaling criteria. Cohesive sediments have different physical properties than sand, and a possibility to avoid such scale effects is to use lightweight m...

The Unazuki Reservoir is located on the Kurobe River, which is influenced by a catchment with one of the highest sediment yields in Japan. Due to a sufficiently available discharge during flood events, annual sediment flushing with full water-level drawdown (i.e., free-flow sediment flushing) is conducted to preserve the effective storage capacity...

Channel confluence is one of the important sections of channel networks which is also common encountered in nature. Six different zones exist at a channel confluence: 1) stagnation zone, 2) flow deflection zone, 3) flow separation zone, 4) maximum velocity zone, 5) flow recovery zone and 6) shear layers between combining flows zone. Due to the comp...

The ANN approach improved the bedload prediction based on ADCP data comparing to the regular linear and non-linear regression analysis. It shows the potential of using machine learning to fulfill the "missing element" in the complex relationship between the bedload and the acoustic scattering.

Many dams around the world are ageing and require upgradation in terms of spillway capacity and other safety aspects. In recent times, challenges faced due to global warming, climate change and cloudburst events have grown not just in numbers but also in extremity. Consequently, several dams and diversion structures are being modified to cope up wi...

Hydro-morphodynamic models are increasingly popular for predicting sedimentation processes in reservoirs. To leverage the accuracy of such models, their boundary conditions have to be defined as precise as possible. While hydrological models provide efficient routines to establish inflow hydrographs at the model boundaries, the determination of the...

The selection of instrumentation for data acquisition in physical model studies depends on type and resolution of data to be recorded, time frame of the model study, available instrumentation alternatives, availability of skilled personnel and overall budget of the model study. The available instrumentation for recording bed levels or three-dimensi...

Recorded presentation: https://youtu.be/LDDONUuKaI4 Visualizing results is more important than ever in scientific dissemination. The analysis and communication of complex phenomena such as flash floods requires new approaches. The target is using a state-of-the-art model with a fast and robust predictive capability, which has been tested in small,...

Despite the many advantages of using active ultrasound sonars, recent studies have shown that the specific acoustic geometry, signal-processing configuration, and complex surface-volume scattering process at the riverbed introduce several uncertainties in bedload estimation. This study presents a comparison of bedload velocity and bottom echo inten...

Two acoustic Doppler current profilers working at three frequencies (3 MHz and 1MHz by Sontek M9 run at three different configurations and 2 MHz by StreamPro RDI) were deployed simultaneously to measure bedload characteristics in a laboratory flume. Seven different transport conditions were simulated using fine gravel and medium sand as sediment be...

Recorded presentation: https://youtu.be/LDDONUuKaI4 The analysis and communication of complex phenomena such as flash floods requires new approaches. The target is using a state-of-the-art model with a fast and robust predictive capability, which has been tested in a small, steep Norwegian river affected by a recent flash flood, and visualizing th...

Within this study the two three-dimensional numerical models SSIIM 1 and SSIIM 2 are used to simulate a physical experiment of a reservoir flushing with partial drawdown of the water level. During the setup of the numerical model, it can be seen that the sluice gate cannot be implemented in accordance with the given conditions in the laboratory exp...

The numerical tools simulating flood events must be accurate, in order to provide useful data, and computationally efficient, to facilitate informed decision-making during a flood. One of the main limitations of modelling software at the present time is the CPU time needed to perform simulations over complex spatial domains. Recent studies show tha...

The numerical tools simulating flood events must be accurate, in order to provide useful data, and computationally efficient, to facilitate informed decision-making during a flood. One of the main limitations of modelling software at the present time is the CPU time needed to perform simulations over complex spatial domains. Recent studies show tha...

Presentation for the conference paper of the same title presented at the 10th International Conference in Fluvial Hydraulics (River Flow 2020). [ABSTRACT] The numerical tools simulating flood events must be accurate, in order to provide useful data, and computationally efficient, to facilitate informed decision-making during a flood. One of the...

The need for effective water resources management has turned into a major challenge, especially in the face of climate change. Meteorological data is not always readily available and thus the task of predicting the response of hydrological systems becomes complicated. For this reason, climate reanalysis datasets are used as a viable alternative. Th...

The flow rate and the suspended sediment concentration (SSC) of two different rivers draining into the Adriatic Sea basin, the Secchia in Italy and the Devoll in Albania, were analysed by processing the data collected in a 245‐days period at monitoring stations equipped with side‐looking acoustic Doppler current profilers (H‐ADCPs). SSC was determi...

This paper provides an evaluation of a hydro-acoustic technique for efficient quantification of the bedload transport in riverine environments. Stationary bedload measurements were conducted simultaneously at different study sites, using three different acoustic Doppler current profilers (ADCP) working at four different frequencies. The raw apparen...

Visualizing results is more important than ever in scientific dissemination. Natural hazards are complex phenomena; their examination and illustration call for a holistic approach when studying them and improving their communication in order to save lives and cost. In this paper, we present an overview of different methodologies ruling the visualiz...

This study aims to develop a surrogate methodology for quantification of the bedload transport in riverine environments by using acoustic devices. Bedload transport experiments were performed in laboratory conditions to test the capabilities of the acoustic current Doppler profilers (ADCP) to quantify the bedload velocity, concentration, and active...

This study aims to develop a surrogate methodology for quantification of the bedload transport in riverine environments by using acoustic devices. Bedload transport experiments were performed in laboratory conditions to test the capabilities of the acoustic current Doppler profilers (ADCP) to quantify the bedload velocity, concentration, and active...

In this study, pressurized flushing of non-cohesive reservoir sediment through a bottom orifice was simulated in laboratory experiments using lightweight material as model sediment. The experiments were carried out by varying flushing discharge, reservoir water level, thickness of sediment deposit layer and opening height of bottom orifice. The vol...

There are many methods available for measurement of bed morphology in physical hydraulic model studies considering mobile bed sediment. Among which, there are sophisticated instrumentations which provide quality results in shorter time but are vastly expensive and requires special training for execution. Whereas the conventional surveying methodolo...

Several studies have investigated the use of the bottom tracking (BT) mode of acoustic current Doppler profilers (ADCPs) for evaluating bedload transport. The raw apparent bedload velocity is usually noisy and contains erroneous data. This study investigates how bedload dynamics influence acoustic processes occurring at the riverbed (i.e., volume a...

Direct discharge measurements during flood events can be challenging from a technical as well as from a safety point of view. Therefore, flood discharges are often estimated by extrapolating a rating curve. Extrapolations far outside the range of the directly measured discharges are common, although the associated errors can be large. In this artic...

Estimates of peak flood discharges are most often based on stage measurements, and the discharge is determined indirectly from the extrapolation of a rating-curve. It is possible to improve the extrapolation of the rating-curve by hydraulic modeling, such as scale or numerical models. In this paper, we discuss a case study for a streamflow gauging...

In recent years, advanced methods for measuring riverbank migration have been used to understand the process of river planform evolution. However, the role of the so-called outer secondary cell in the hydraulic pattern in bank erosion remains unclear. For this purpose, a natural river meander with high curvature bends and steep riverbanks was chose...

This work aims to investigate the possibility of using the acoustic backscatter from riverbed at two well-spaced approaching angles (i.e., 70° and 90°) of the acoustic beam to river bottom (i.e., grazing angle) to characterize the sediment layer moving close to the riverbed.

The bottom tracking (BT) feature of the acoustic Doppler current profilers (ADCP) has emerged as a promising technique in evaluating the bed load. Strong statistical correlations are reported between the ADCP BT velocity and the transport rate obtained by physical sampling or dune tracking; however, these relations are strictly site-specific, and a...

The present study documents the successful application of a Reynolds-Averaged Navier-Stokes model with conventional turbulence closure to calculate discharge coefficients for submerged flow conditions at ogee-type weirs. The flow pattern downstream of submerged weirs is complex. At low submergence, there is a plunging jet and submerged hydraulic ju...

Monitoring stations in rivers and water courses are an important mean to obtain critical data about the different variables that play a role in the hydrodynamics and ecological processes. Measuring suspended sediment concentration often requires the displacement of equipment and manpower to the field. This is often expensive and not practical, in p...

This study presents a series of acoustic current Doppler profiler (ADCP) measurements, which are converted into suspended load concentrations (SSC). Depending on the particle size distribution (PSD), the sound backscatter and its attenuation are used to determine a theoretical minimal and physical upper limit of the SSC. The SSC are displayed over...

Physical models are a well-accepted tool in hydraulic engineering, allowing for the detailed characterisation of flow processes and the validation of structure designs with complex boundary conditions. The methods used to construct physical models typically produce a surface roughness which does not necessarily scale with the surface roughness of t...

The bottom tracking (BT) feature of the acoustic Doppler current profilers (ADCP) have emerged as a promising technique in evaluating the bed load. Strong statistical correlations are reported between the ADCP BT velocity and the transport rate obtained by physical sampling or dune tracking; however, these relations are strictly site-specific and a...

The catchment of the Dashidaira reservoir located on the Kurobe River has high sediment yield. Because of the sufficient available amount of water in the catchment during flood events, the free-flow sediment flushing operation with full water-level drawdown is employed every year to preserve the effective storage capacity of the Dashidaira reservoi...

Denne rapporten inneholder en oppsummering og dokumentasjon på det arbeidet som er utført i prosjektet HydroPEAK i CEDREN. Bakgrunnen for etableringen av CEDREN var klimaforliket i Stortinget i januar 2008, som igjen førte til økt satsing på fornybar energi, og etter hvert etablering av flere forskningssenter for miljøvennlig energi (FME). På denne...

The metadata of the Norwegian historical topographic maps are given, in order to make its georeference possible, using just their corners points as control points. The earliest systematic topographic map product is the square mile-maps (kvadratmil kart). They cover the southern leg of the Swedish border region of Norway as it was in the end of 18 t...

The 1:50,000 and 1:100,000 scale historical sheets of the Norwegian topographic 'Rektangelkart' map series were georeferenced, in order to obtain the original hydrography of the Gaula River, at a ca 50 kilometer long section between Støren and the estuary to the Gulosen Bay. The 1:50,000 scale sheets are the earliest systematic topographic works of...

The poster presents the numerical modelling of the hydromorphological evolution of a 10-km reach of the Po River close to Ostiglia in Italy, affected by the presence of two bridges.

The paper presents the numerical modelling of the hydromorphological evolution of a 10-km reach of the Po River close to Ostiglia in Italy, affected by the presence of a railway bridge. The 3D simulation is performed using the freely available code SSIIM, developed at the University of Science and Technology in Trondheim in Norway. The domain consi...

The reliable prediction of morphological changes of rivers is of major need in the field of river engineering. Besides the conventionally used empirical procedures or hydraulic scale models, the numerical modeling is a progressively developing, but still not a widespreadly used tool. Moreover, the sediment transport modeling at non-uniform river be...

The use of acoustic and optic devices has become more and more common for estimating suspended sediment loads in rivers. The echo intensity levels (EIL) recorded by means of an Acoustic Doppler Current Profiler (ADCP) have been applied in different methods, which provided relationships between scattering particles features derived from samples (i.e...

3D numerical models are increasingly used to simulate flow, sediment transport and morphological changes of rivers. For the simulation of bedload transport, the numerical flow model is generally coupled with an empirical sediment transport model. The application range of the most widely used empirical models is, however, often limited in terms of h...