Dune dynamics and preservation in the River Waal using Multibeam and Parametric Echo Sounding (PES) [Acronym: PES-Waal]
River dunes occur in low-land rivers worldwide and are vital in estimating sediment transport and deposition within fluvial systems. Dune sizes and mobility vary and therewith may interfere with inland shipping and affect sediment (bedload) fluxes. Analysing bed morphodynamics allows for determining spatio-temporal variations in size and migration rate of individual dunes, as well as the longterm, large-scaled trends in bed elevation. However, merely dune tracking does not fully explain sediment storage/reactivation in river systems. Observing sedimentary structures in the shallow subsurface will enable us to reconstruct the preservation and reactivation of river dunes over time.
This project aims to collect high-resolution Parametric Echo Sounder (PES) data of the subsurface of dunes in the River Waal, Netherlands, simultaneously with multibeam data and sediment vibrocores, and to interpret internal dune structures, to - in a later phase - be able to couple these structures to morphodynamics as obtained from multibeam (MBES) time series.
The project will result in knowledge of river systems and new technical know-how on applying the PES technique in Dutch rivers. This knowledge can be used for quantifying sediment dynamics for river management, improving numerical models with bed roughness and sediment supply predictors and for improving shipping safety
Doel van het project
The aim of this project is to generate new fundamental knowledge on the spatial and temporal variations in the preservation and reactivation of river dunes in the subsurface of the river Waal. The time scales that are involved will follow from this research. This project will contribute to the understanding of sediment transport and deposition processes in rivers and the long-term behaviour of rivers.Hereto the main project objectives are:- to research the applicability of innovative geophysical techniques in two field surveys in time in which we combine high-resolution parametric echo sounding (PES) data with simultaneous multibeam echo sounding (MBES preferably bathymetric and backscatter) data and sediment cores (cores only with the second survey) for future linking of internal dune structures to their morphodynamics and sediment characteristics.- to analyse the PES data- to establish dune preservation and reactivation from observed internal structures of each of the PES-surveys and in the period between the two surveysSince to our knowledge this is the first time that PES will be conducted in Dutch rivers we will test the performance of PES in three different parts of the Waal with varying grain sizes (e.g. gravel/sand/finer sediments) but more importantly the three sites are selected to investigate the role of grain-size distribution in flow and bed dynamics upstream and downstream. Furthermore we will conduct two PES surveys in time in order to estimate what temporal scales play a role in the dune dynamics and their preserved internal structures.The PES survey sites and timing will be attuned to the ongoing multibeam monitoring so that the new datasets flawlessly fit in the longer time series and will be co-ordinated by Van den Herik and Rijkswaterstaat. The sub-bottom PES data will be accompanied by vibrocoring for geological verification and grain size analyses in the lab. Coring locations and timing will again have to be attuned with
Dune dynamics and preservation in the River Waal using multibeam (MBES) and parametric echo sounding (PES).River dunes are common in most low-land rivers in the world including the Dutch rivers (Fig. 1) and play a central role in sediment transport and deposition processes (Kleinhans 2001 Best 2005). The variability in dune height and dynamics depends on parameters such as discharge (Julien and Klaassen 1995 Wilbers and Ten Brinke 2003 Cisneros et al. 2019) and determines the navigability of rivers (e.g. Amsler and Garcia 1997 www.covadem.org).Figure 1: Bathymetric map showing bedforms in the Waal near Waardenburg.Although river dunes have been studied extensively (e.g. Kleinhans 2002 Best 2005 and references therein Cisneros et al. 2019) and although net sediment budgets due to downstream migrating dunes can be estimated from dune tracking (Wilbers and Ten Brinke 2003) net volumes as calculated from the net changes in bed level in MBES time series do not fully explain the bedload sediment fluxes in rivers nor how much sediment is being stored (preserved) in the river bed or what time scales are involved.Dune preservation is crucial in the understanding of the spatial and temporal variations in sediment transport and deposition rates in rivers (i.e. KIA and NKWK questions) and can be studied from internal dune structures (Paola and Borgman 1991 Leclair and Bridge 2001 Reesink et al. 2015 Van de Lageweg et al. 2016). Using the high-resolution acoustic technique Parametric Echo Sounder (PES) we may observe the internal structures and reactivation (erosion) surfaces of bedforms in the subsurface of river beds (Sambrook Smith et al. 2013 and Fig. 2: unpublished data by courtesy of J. Best). Figure 2: Example of sub-bottom PES data of internal structures of bedforms and reactivation surfaces in the Mekong river Cambodia. For scale: one block in the grid is 10 m horizontally and 1 m vertically (Figure remains copyright of Jim B
Work package 1: design of PES surveys acquisition of PES and MBES data and coring:(Dec 2019 – Nov 2020)
- to assemble existing data: complete bi-weekly high-resolution MBES time series of the Waal that we already have available for 2005-2015 between Slijk-Ewijk and Ochten previous grain size data hydrodynamic data from Rijkswaterstaat and geological data of the Waal (e.g. TNO’s DINO-database)
- to preliminary analyse selected multibeam datasets of the bi-weekly time series for the purpose of designing the PES surveys
- to design the PES surveys (sites estimate of period between two PES surveys route speed etc)
- to conduct the field surveys these are planned early in the project and to fit into the ongoing MBES monitoring.
- to collect 18 vibrocores with the 2nd PES survey based on the preliminary observations of the 1st PES survey to plan locations
Work package 2: data analyses:(Mar 2020 – Mar 2021)
- preliminary analysis of river dune dynamics of selected MBES bathymetry time series. (budget limit constrains us to processing the newly acquired MBES bathymetry data in WP1 and a small number of existing datasets)
- analysis of PES data acquired in WP 1
- if MBES backscatter was successfully acquired in WP1 processing the backscatter data
Work Package 3: interpretation of results:(Sep2020 – Dec 2021)
- to interpret sedimentary structures in the shallow subsurface and establish dune preservation and reactivation from observed internal structures of each of the PES-surveys and in the period between the two surveys
- if MBES backscatter was successfully acquired in WP1 river bed sediment classification of backscatter data (The coupling dune preservation from PES data to dune morphodynamics from the bi-weekly MBES time series is future research intended in ‘TKI phase 2’ to be applied for in 2020.)
Work Package 4: reporting and dissemination:(Mar 2021 – Dec 2021)
- writing up final project report
- abstract presenting
1. New technique new knowledge and new in the Netherlands – yet proven to be successful elsewhere:PES was never used in Dutch rivers before to investigate the preservation of river dunes. PES was applied by Prof. Best’s team in the Ríos Bermejo and Paraná Argentina (Sambrook Smith et al. 2013 Sambrook Smith et al. 2016) and the Mekong river Cambodia (see Fig. 2 as for yet unpubl. data of J. Best) and was demonstrated to be successful as a technique in sandy and finer sediments. If we manage to collect also multibeam backscatter data (in addition to the MBES bathymetry) then we can make a high-resolution map of bed sediment types that cannot be done with the classical (currently used) method using sampling. To date in the NLds shorter MBES time series were used to analyse the net bed level differences and dune tracking in order to calculate net bedload transport volumes. Dune preservation in the subsurface provides crucial insight for reconstructing true bedload transport and deposition processes and what time scales (storage times) are involved. This new approach not only means adding crucial (and to date missing) information for studying sediment transport in Dutch rivers butalso provides us with a new type of data and new insights in river dune preservation and reactivation in river systems not existing in the Netherlands so far. Hence this project ‘imports’ this knowledge to the Netherlands in a valuable knowledge transfer through superb international collaboration with knowledge institutes government and industry thereby strengthening our knowledge position in Delta Technology.2. Unique-in-the-world datasets towards 3D and an unprecedented handle on time:The combination of morphodynamics of the bed (2-D surface) PES (looking into the subsurface) in time series and sediment cores to interpret the sub-surface data makes this approach unique in the world (not in any river was this combination of data ever acquired). This approach l
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De informatie over dit project wordt kenbaar gemaakt via de website van de TKI Deltatechnologie (projectbeschrijving) en de projectwiki van Deltares (projectvoortgang en resultaten).
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