Hydraulic analysis of a flood channel from the Afgedamde Maas to the Biesbosch and Bergse Maas

Hydraulic analysis of a flood channel from the Afgedamde Maas to the Biesbosch and Bergse Maas

Winkelhorst, J.

Vrijling, J.K. (mentor)
Uijttewaal, W.S.J. (mentor)
Kok, M. (mentor)
Duits, M. (mentor)
Stijnen, J.W. (mentor)

Civil Engineering and Geosciences

Hydraulic Engineering

River Engineering

2013-01-29

Due to climate change, it is expected that the design river discharge of the Rhine will increase from 16000 m3/s in 2015 to 18000 m3/s in 2100. In order to make the Dutch water system climate proof, dikes must be reinforced and raised and/or the design water level must be lowered. In this study, a flood channel as a measure to decrease water levels has been investigated, and has been compared to dike reinforcements. The investigated flood channel runs from the Afgedamde Maas towards the Biesbosch and Bergse Maas. This flood channel has been designed by architect Robbert de Koning, and is part of a larger plan to make the Dutch lower rivers climate proof until the year 2100. The length of the flood channel is approximately 20 kilometers, and the flow width is 600 meters. The flood channel is designed for a use of once every hundred years. The flood channel has been analyzed first by a simple one-dimensional model, in order to get a first estimation of the results. The second step was to model the flood channel in a two-dimensional model. This model is based on the WAQUA Rhine-Maas Estuary model, calibrated for the Hydraulic Boundary conditions 2011 (RMM-HR2011 model). This two-dimensional model has been updated to the reference year 2015. In order to add the flood channel, a new numerical grid has been created, because the flood channel lies outside the existing numerical grid. At a 18000 m3/s Rhine discharge, the flood channel’s discharge is 2707 m3/s (23% of the Waal’s discharge). As a result, the discharge through the Amer increases up to 32%, while the discharge through the Nieuwe Merwede decreases up to 28%. The maximum water level decrease at the Waal is approximately a meter, and the maximum water level increase at the Maas is 0.44 meter. The results showed that the performance of the flood channel is significantly lower than the expectations, and that the lower performance of the flood channel is mainly caused by the discharge capacity of the outlet channels. Based on the water level results and flood channel design, the costs have been calculated. The calculated costs for the flood channel are 1567.6 million euros. The cost-efficiency is estimated on 18 m2/106 €, which is low for such a large measure. Due to the flood channel, the costs for dike reinforcements until the year 2100 are reduced with 266 million euros. However, practical limits to dike reinforcements and values related to landscape, nature and culture are not taken into account, which is expected to change the cost-benefit balance. Based on the water level results and costs calculations, the investigated flood channel is not hydraulically optimal, and not a cost effective alternative for dike reinforcements. However, hydraulic optimization of the channel is possible, and when values of landscape, nature and culture would be taken into account, the cost effectiveness could be more positive.

flood channel
hydraulic
climate change
Delta program

http://resolver.tudelft.nl/uuid:05da335c-f54d-4f98-ba39-d6861f74c5fe

2013-01-30

Student theses

master thesis

(c) 2013 Winkelhorst, J.