Toepassen van duikers in kaden in uiterwaarden

Toepassen van duikers in kaden in uiterwaarden

Wilms, T.

de Vriend, H.J. (mentor)
Havinga, H. (mentor)
Sloff, C.J. (mentor)
Baptist, M.J. (mentor)
Beckers, J.V.L. (mentor)

Civil Engineering and Geosciences

2006-01-01

In 1993 and 1995 the Netherlands were started by two flood waves. They did not cause much damage in the floodplains, but they made clear that it should not be taken for granted that the Netherlands are protected for floodings. Therefore in 1996 the policy 'Ruimte voor de rivier' came to effect. In this policy measures are sought to protect the Netherlands during flood waves. One of the measures is the lowering of the hydraulic roughness in the floodplains, so the fall is decreased. The hydraulic roughness of the dikes in the floodplains can be decreased, for example by letting water flow through the dikes (through culverts). These dikes are elevations, which connect the summer dike and the winter dike, they lay perpendicular to the current. The problem of many measures is the uncertainty of the effect during a flood wave, this applies for this measure as well. It is important to know how much the water level lowers if culverts are used in the dikes in the floodplains. After this effect is studied, the measure can be applied in the floodplains. The objective is to get insight in the flow of water around a dike with a culvert. Three questions are posed: - What is the effect of the use of culverts in dikes in the floodplain? - Is the fall caused by the construction as a whole equal to the addition of the separate fall caused by the current through the culvert and the current over the crest? - Is there a relation between (hcrest/hculvert) and (ucrest/uculvert) or (qcrest/qculvert)? The first step is literature research for the hydraulic roughness of dikes and the occurrence and efficiency of culverts. These were found and the constructions can occur in different flow regimes: free flow and fully submerged flow. Each regime has different discharge coefficients. To get more insight in the effect of the measure, with the WAQUA-model of Rijkswaterstaat (a 2D-flowmodel) the removal of two dikes in the floodplain is simulated in the project area, the Beuningse Waard near Nijmegen. During a flooding the water level decreased 0,0085 meter. This small lowering is caused by situation in the floodplain; present obstacles have a negative influence on the effect of the measure. The complete removal of the two dikes is a useful measure for 'Ruimte voor de rivier' due to low costs. The use of culverts in the dikes in the floodplain is not useful; the effect decreases and the costs increase. Subsequently fall and flow are measured for different scale models in a flume in the fluid mechanics laboratory. Constructions with different culvert heights are used to determine the discharge coefficients. The scale models had a slope of 1:3 and a fixed crest height, 0,20 meters above the bottom. The bottom of the model is removed in steps of 0,05 meters, to simulate the effect of a culvert. The experiments are per unit of width. With the results of the experiments the research questions can be answered: - The use of culverts in dikes in the floodplain has effect. With a constant discharge this effect decreased when the water level downstream increases. For all flow regimes the effect of the measure can be calculated. - The addition of the fall of the separate currents is allowed. - The relation between flow through the culvert and over the crest is: 1,2 uculvert = ucrest

culverts
dikes
floodplain

http://resolver.tudelft.nl/uuid:61b8c607-69b2-49e2-a303-57061a22a114

TU Delft, Civil Engineering and Geosciences, Hydraulic Engineering

Student theses

master thesis

(c) 2006 T. Wilms