Becker, Marius

Grünler, Steffen

Maushake, Christian

Winter, Christian

English

Hydraulic Engineering Repository

Conference Paper, Published VersionBecker, Marius; Maushake, Christian; Grünler, Steffen; Winter, ChristianEvaluation of ship-based Sediment flux measurements byADCP's in tidal flowsVerfügbar unter/Available at: https://hdl.handle.net/20.500.11970/110806Vorgeschlagene Zitierweise/Suggested citation:Becker, Marius; Maushake, Christian; Grünler, Steffen; Winter, Christian (2017): Evaluationof ship-based Sediment flux measurements by ADCP's in tidal flows. In: GeophysicalResearch Abstracts, Vol. 19, EGU2017-16110, 2017. EGU General Assembly 2017.https://meetingorganizer.copernicus.org/EGU2017/EGU2017-16110.pdf.Standardnutzungsbedingungen/Terms of Use:Die Dokumente in HENRY stehen unter der Creative Commons Lizenz CC BY 4.0, sofern keine abweichendenNutzungsbedingungen getroffen wurden. Damit ist sowohl die kommerzielle Nutzung als auch das Teilen, dieWeiterbearbeitung und Speicherung erlaubt. Das Verwenden und das Bearbeiten stehen unter der Bedingung derNamensnennung. Im Einzelfall kann eine restriktivere Lizenz gelten; dann gelten abweichend von den obigenNutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte.Documents in HENRY are made available under the Creative Commons License CC BY 4.0, if no other license isapplicable. Under CC BY 4.0 commercial use and sharing, remixing, transforming, and building upon the materialof the work is permitted. In some cases a different, more restrictive license may apply; if applicable the terms ofthe restrictive license will be binding.Geophysical Research AbstractsVol. 19, EGU2017-16110, 2017EGU General Assembly 2017© Author(s) 2017. CC Attribution 3.0 License.Evaluation of ship-based sediment flux measurements by ADCPs in tidalflowsMarius Becker (1), Christian Maushake (2), Steffen Grünler (2), and Christian Winter (1)(1) Marum - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany, (2) BAW - FederalWaterways Engineering and Research Institute, Hamburg, GermanyIn the past decades acoustic backscatter calibration developed into a frequently applied technique to measurefluxes of suspended sediments in rivers and estuaries. Data is mainly acquired using single-frequency profilingdevices, such as ADCPs. In this case, variations of acoustic particle properties may have a significant impact on thecalibration with respect to suspended sediment concentration, but associated effects are rarely considered. Furtherchallenges regarding flux determination arise from incomplete vertical and lateral coverage of the cross-section,and the small ratio of the residual transport to the tidal transport, depending on the tidal prism. We analyzed foursets of 13h cross-sectional ADCP data, collected at different locations in the range of the turbidity zone of theWeser estuary, North Sea, Germany. Vertical LISST, OBS and CTD measurements were taken very hour. Duringthe calibration sediment absorption was taken into account. First, acoustic properties were estimated using LISSTparticle size distributions. Due to the tidal excursion and displacement of the turbidity zone, acoustic properties ofparticles changed during the tidal cycle, at all locations. Applying empirical functions, the lowest backscatteringcross-section and highest sediment absorption coefficient were found in the center of the turbidity zone. Outside thetidally averaged location of the turbidity zone, changes of acoustic parameters were caused mainly by advection.In the turbidity zone, these properties were also affected by settling and entrainment, inducing vertical differencesand systematic errors in concentration. In general, due to the iterative correction of sediment absorption along theacoustic path, local errors in concentration propagate and amplify exponentially. Based on reference concentrationobtained from water samples and OBS data, we quantified these errors and their effect on cross-sectional averagedconcentration and sediment flux. We found that errors are effectively decreased by applying calibration parametersinterpolated in time, and by an optimization of the sediment absorption coefficient. We further discuss practicalaspects of residual flux determination in tidal environments and of measuring strategies in relation to site-specifictidal dynamics.

Evaluation of ship-based Sediment flux measurements by ADCP's in tidal flows

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Evaluation of ship-based Sediment flux measurements by ADCP's in tidal flows

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