Structured block ramp – basic tests

The first model investigations concerning structured block ramps were made for the River Emme case study. Structured block ramps were chosen to replace the ecological barriers (see River Emme case study). Consecutively similar investigations were performed in a smaller channel (Fig. 1). Additional investigations were conducted to quantify the influence of the undulated discharge and the sediment transport rate to the ramp stability. These tests aim to find an optimum combination of step length, pool depth and ramp slope. No restrictions concerning the step height in the basic investigations were made in contrast to the River Emme case study, where the difference between the steps was unvaried because of the ecological criteria.

A slope region between 3.9 % and 7.9 % and ratios of step lengths to pool depth between 8 and 24 were investigated. The discharge was increased staircase like such that the steps were likely to collapse as shown in Figure 2 and 3.

The present examination shows that single steps risk to collapse if the wave and step length vary in extension. The results of the basics investigations will be compared to results of model tests concerning river bed stabilisation with transverse rib structures.