Sluice structures are common in the Netherlands both on smaller watercourses to control fluvial flooding and on the large flood defence structures separating the inland seas from the North Sea, to guard against tidal flooding.
Traditionally the structures have concrete aprons to prevent scour and loose rock beyond the aprons. Over the years there have been examples of mechanical failure of individual gates which can then result in excessive flows rates in localised areas, which in turn result in scour beyond the aprons. Hesselberg Hydro have worked on a programme of upgrading several structures, using bituminous grout placed underwater to stabilise the rock beyond the aprons.
With Lock structures, loose rock can cause problems by blocking gates and interfering with the operation of the sluice gates so again we have been working on a programme of upgrading the most vulnerable structures.