CHR Spring Seminar

Background

The Rhine River is the most important waterway in Europe. It connects the port of Rotterdam with inland industrial areas. Bed evolution of the Rhine River by erosion and sedimentation has been studied for years based on bed level surveys and transport measurements of bed load and suspended load. The subtraction of bed level data from two different time periods shows whether the river bed is subject to erosion or sedimentation, which is the most essential morphological information needed by river managers. Transport measurements also provide information on the types of sediments involved (e.g., gravel or sand) and on the mechanism of sediment transport (suspended load or bed load). However, both echo soundings and transport measurements fail to provide answers to essential questions such as: (1) Where are the sediments transported by the river coming from?, (2) Where are the eroded sediments going to? and (3) How is the morphological development in one part of the catchment linked to changes in other parts of the catchment? This kind of information is crucial for a real understanding of a river system and for optimizing sediment management strategies. It can only be obtained through the construction of a sediment budget, which is the balance between the amount of sediment entering a study area, the amount of sediment leaving the study area and the (change in) sediment storage in the study area itself.

In a joint research project, the Federal Institute of Hydrology and the RWTH Aachen University developed a sediment budget of the Rhine River from the source to the mouth, differentiated for size fractions stones, coarse gravel, fine gravel, sand and fines (silt and clay). During the seminar, the sediment budget is presented and gaps in knowledge and uncertainties are discussed. Special focus will be on sources and sinks of different grain size fractions and their impact on the sediment budget and the river bed evolution.

Objectives

• to discuss potential consequences of the sediment budget analysis on river management
• to identify gaps in knowledge on sediment transport processes within the Rhine catchment
• to assess methods to reduce uncertainties, e.g. in load measurements