Nautical bottom sediment research: Sub report 8. Sediment parameter evolution in the STT

The Sediment Test Tank (STT) has been built on the terrain of Flanders Hydraulic Research (FHR) to host in-situ sediment for sediment studies. After delivery (16/04/2009) of 50 m³ of sediment from the harbour of Zeebrugge at a density of 1.14 m³/s, sedimentation and consolidation created vertical differences in the sediment in the STT. The measurements started on 21/04/2009. This report deals with the measurements until 26/05/2010.A whole range of parameters have been measured over time and depth to monitor the sediment characteristics as much as possible. Some parameters are measured in situ in the tank, e.g. measurements by the YSI-multiparameter probe and pore pressure measured by piezometric tubes. Other parameters are measured on undisturbed samples, e.g. density, rheological parameters and thermo-gravimetric analysis. This report gives the findings of the measurements and recommendations for further measurement campaigns in the STT

Experimental investigation on consolidation behavior of mud: Subreport 1. Methodology study

Due to the complex nature of mud consolidation within harbours, a robust and accurate guideline to evaluate the nautical depth is still under debate. Besides, alternative dredging techniques (e.g. mud conditioning/fluidising) have proven to be an applicable method to reduce dredging costs in a number of harbours. Yet, before one can define new criteria for nautical depth or implement new dredging techniques, a deeper understanding of the temporal evolution of rheological, mechanical and biological characteristics of mud is needed. In this study, we aim to improve the understanding of the rheological properties of consolidating mud by comparing the consolidation process of mud from 5 different locations namely the harbours of Zeebrugge (ZB) and Deurganckdok (DG) in Belgium, the harbours of Rotterdam (RO) and Ijmuiden (IJ) in the Netherlands and the Emden (EM) harbour in Germany. The main objectives of this project are to examine the effect of the consolidation process on the mechanical, rheological and biological characteristics of mud as well as to explain the differences in consolidation processes between muds from different origins.This sub-report describes the properties of different mud types used for the experiments as well as the experimental setup. The experimental setup includes a detailed description of the governing parameters, experimental design and measurement techniques conducted on two different consolidation columns, small and large

Nautical bottom sediment research: Sub report 11. Cohesive sediments dimensional analysis

The dimensional analysis technique was applied in order to determine possible relationships between the measured parameters in the STT and to identify possible inconsistencies in the measurements.The present dimensional analysis focuses only in the sedimentation and consolidation processes.Relationships between parameters could be used to identify inconsistencies for measured pore pressure, effective stresses and density values. Recommendations are suggested for sampling points and measuring methods

Continuous grid monitoring to optimize sedimentation management

Fluves and GTC monitor since November 2015 continuously a sediment trap with dimensions 200 x 20 meters managed by the Flemish Environmental Agency (VMM) in Belgium. The continuous follow-up of sedimentation of the trap provides insights on temporal and spatial evolution of trapping efficiency. VMM will use the insights to optimize operational dredging decisions and for optimizing the design of future traps. The installed measuring system is based on distributed temperature sensing with a fiber optic cable of more than 2 km. A digital terrain model (DTM) of the sediment trap is transmitted to the client on a hourly to daily basis. Results after winter floods from November 2015 till February 2016 show a significant spatial variation in sedimentation through the sedimentation trap. Also, zones with different temporal evolution of filling of the trap could be observed. The technique shows great potential for detailed spatial and temporal observation of sedimentation processes in large areas, as well as the ability to detect thin sedimentation layers

SWOT analysis of breach models for common dike failure mechanisms

The use of breach models includes two tasks: predicting breach characteristics and estimating flow through the breach. Strengths and weaknesses as well as opportunities and threats of different simplified and detailed physically-based breach models are listed following theoretical and practical criteria. According to the theoretical criteria, the breach models that incorporate detailed breaching processes offer more opportunities. In practice however, these models do not necessarily give rise to better results. From the SWOT-analysis, it can be concluded that consolidation of present knowledge towards a comprehensive breaching theory is far from complete. For flood risk analyses, the challenge remains to find equilibrium between detailed process description and practical model implementation and calibration. Nowadays, some modelling suites are black-box models. Others have numerous modelling options that do not improve transparency. Moreover, all models lack validation for real-world case studies, especially for composite dike typesHydraulic EngineeringCivil Engineering and Geoscience

Erosion modelling towards, and sediment transport modelling in unnavigable watercourses in Flanders, Belgium

Antea Group and KULeuven were awarded a project in Flanders to identify the regions exporting high sediment loads to unnavigable watercourses and the sedimentation zones within them. Two types of models are applied: hydrological sediment export models (SEM) and hydraulic sediment transport models (STM). The influence of erosion control measures on sediment export as well as river engineering measures needs to be taken into account. A concept will be developed to connect the SEM and STM, enabling the sediment to be routed from upstream to the sedimentation zones. Results of the study will be used by the Flemish government to plan erosion control measures, estimate future sedimentation volumes, steer sedimentation and optimize river engineering and dredging works. Finally, model results could also be used to obtain better insights to the re-suspension risks of contaminated sediment in watercourses