This research combines hydromorphological field measures and hydrological and transport sediment modelization in two stream restoration case studies: 1. Oostrumsche beek stream and 2. Leuvenumse beek stream.
The project in the Leuvenumse beek is characterized by the introduction of dead woody debris patches and sand suppletion sites, which result in flow heterogeneity, habitat diversity and reconnection of the incised channel with the riparian zone through the sand suppletion. The project in the Oostrumsche beek consists of a channel diversion, of which the normalised and channelised stream is diverted through an alder swamp forest in the former stream valley.
I performed with the model HEC-RAS an one-dimensional steady flow and a quasi unsteady flow combined with sediment transport-mobile bed for both cases. The hydraulics parameters required by the sediment transport calculations were extracted from the calibrated steady model. Most of the calibration errors for bed channel and water surfaces elevations are below five centimeters in both case studies.
The prediction of the deposition and the erosive zones and its associated current velocities in both studied cases can delimitate the areas within restored streams are likely to contain suitable habitats for specific species (plants and animals). In this way an optimization of cost-effective methods for sampling and sample processing in biomonitoring programs is improved. This is especially important monitoring with BACI-designs. The research reveal the importance of knowing the grain sizes distribution of the sand added to the stream during the sand suppletion and the distribution of the dead woody debris patches.