Hydraulic impact of a real time control barrier at the bifurcation points

ABSTRACT: Without flood defences much of the Netherlands would be flooded (by the sea or the river) on a regular basis. Along the full length of the river Rhine and along parts of the river Meuse protection against river flooding is needed. This protection is provided by flood defences (mainly dikes). The river Rhine has in the Netherlands two bifurcation points, the Pannerdensche Kop and de IJssel Kop. There are at this moment no regulators at these points and the distribution of the discharge is a result of natural processes. The safety against flooding downstream these bifurcation points is highly dependent on the result of the discharge distri-bution. In the design of the flood defences there is, according to design guidelines, assumed that the discharge distribution over the branches is completely certain. However the discharge distribution at the design fre-quency is never observed so the uncertainty is considerable. This uncertainty that is unaccounted for in the design of the river dikes increases the failure probability. In this paper we will present a study of a real time control barrier at the two bifurcation points, using a one-dimensional hydraulic model. The objective of these barriers is to reduce the deviations of the distribution and therewith the uncertainty. It is shown that for some of the disturbances of the water distribution a control barrier might be helpful, but it cannot be shown to be ef-fective for all cases. The results also depend on the control criteria (for example the average disturbance of water levels along one of the branches or the maximum disturbance) and on the control objective (concentrate the discharge on one of the branches where damage of flooding is lower than the other branches, or minimize the disturbance on all branches as much as possible).