An interdisciplinary and multicriteria design process was developed to optimize navigation and environmental objectives for the Madeira River in Brazil. A fluvial geomorphology study identified development reaches based on geologic stability with an average periodicity of 57 km. A low water reference plane (LWRP) was established representing a 90% exceedance stage based on bathymetric data collected from the Brazilian Navy and a combination of hydrological analysis and hydraulic modeling. Critical shoals and rock outcrop locations were identified based on a proposed 3.6 m draft at the LWRP. Channel dimensions were established based on Brazilian design criteria with the goal of minimizing potential repetitive maintenance dredging and allowing for adaptive management of the navigation channel location. All but one of the 17 critical navigation sites were located in the upper 640 km of the Madeira River, and site-specific designs using river training structures (dikes) were developed at 4 of the sand shoal locations. These designs were analyzed using a one-dimensional sediment transport model in HEC-RAS to evaluate the potential self-scouring response at the river training structures. The final masterplan includes beneficial reuse of large woody debris for temporary river training structures, permanent (rock) river training structures, rock removal, maintenance dredging with strategic placement to promote channel self-scour, aids to navigation, adaptive channel management, and the development of a national monitoring plan.

@en

Groynes have been replaced by longitudinal training walls in an 11-km long pilot project to optimize training of the river Waal in the Netherlands. These train­ ing walls improve navigability, reduce flood levels, create a sheltered second channel with more favourable ecological conditions, and decrease the erosive action on the river bed that is responsible for large-scale bed degradation. River managers wish to assess whether longitudinal training walls could have similar advantages along other parts of the Dutch Rhine branches (without excessive increase of maintenance costs). The required maintenance dredging depends on the amount of sediment entering the sheltered channel over an entrance sill situated at the upstream edge of the longitudinal training wall. Currently operational morphodynamic models cannot reliably compute this sedi­ ment flux. We present laboratory experiments to study the passage of bed sediment at different discharge distributions between the main and sheltered channel, and different degrees of submergence.@en

Longitudinal training walls are man-made river dividers. They were built in the Netherlands as a replacement of perpendicular groynes as a river training alternative to decrease flood risk and stop the ongoing bed degradation, while still allowing safe navigation. The efficiency of these structures relies on the long-term stability of the two channels on either side of the walls. Sediment and flow distribution are mainly controlled by a sill that behaves as a side weir at the upstream end of the walls. Research conducted to understand the morphodynamic behavior of these sills concludes that three-dimensional flows are present and that their impact on sediment transport still needs to be investigated. This paper presents the historical events that led to the construction of the longitudinal training walls in the Waal River located in the Netherlands, a literature review of previously conducted research and the questions that still need to be addressed in future research to describe the sediment transport over the sill.@en