In this research an effort is made to contribute to the goals of the Betonakkoord. This is done by optimising the design of big and bulky structures consisting out of a lot of concrete, namely lock heads. Lock heads are part of the navigation lock. The main research question answered in this thesis is phrased as follows: How can the design of lock heads be optimised to increase the sustainability?
Different alternatives have been generated to try to increase the sustainability. Each alternative has been compared to the lock head in Empel to test their feasibility. The following alternatives are considered: Inhomogeneous cross section, Prestressing and Hollow sections. From the alternative study it becomes clear that none of the alternatives are effective. The alternatives show no significant decrease in cost and MKI. Therefore, the alternatives are neglected in the remainder of the research. Based on this conclusion the following question arises: Is it possible to increase the sustainability of a lock head design based on commonly used design rules? In the next step of the research a parametric model is developed in order to answer this question. The parametric model design is based on the rules prescribed by the 'Handboek voor het ontwerpen van Schutsluizen' and the 'Richtlijnen Vaarwegen 2017'. The parametric model takes into account two types of gates, being a single leaf gate and a mitre gate. Again, the lock head in Empel has been used to validate the parametric model. From the parametric model it follows that in general a mitre gate is more cost effective and sustainable than a single leaf gate. This is because a mitre gate is generally shorter than a single leaf gate, so less materials are used and the construction pit can be smaller. Furthermore, the parametric model shows that the global stability check horizontal bearing capacity is a key parameter in the design of a lock head. To account for the horizontal bearing capacity the length and the weight of the lock head are important factors. The next step is to compare the lock head designs from the parametric model with the lock head design in Empel. The lock head design in Empel deviates from the rules prescribed by the 'Handboek voor het ontwerpen van Schutsluizen'. By deviating from the rules a more cost effective and sustainable design is acquired than both the designs from the parametric model. The lock head in Empel is shorter and lighter than the lock head designs from the parametric model. This is due to the fact that the lock head in Empel derives its horizontal bearing capacity from the lock chamber. In order to design a more cost effective and sustainable lock head it is advised to incorporate the lock chamber in the stability calculations. Hereby a shorter lock head can be achieved.

The Clarence River catchment is located in the state of New South Wales (NSW), on the east coast of Australia. The lower Clarence Valley is an area covering approximately 1000 square kilometers and is located on the downstream part of the Clarence River. Due to heavy rainfall, the Clarence River discharge can increase from an average 160 m3/s to 20000 m3/s. As a result, water levels rise significantly leading to severe floods in the Clarence Valley. The main urban areas in this region, Grafton, South Grafton and Maclean, are located in narrowing river bends which makes them particulary vulnerable to flooding during high water levels.

The main goal of this report is to present flood mitigation measures to reduce the impact of flooding in the urban areas of the Clarence Valley, based on the Duthc flood mitigation strategy called 'Room for the River'. Consequently the following research question was formulated:

How can the impact of flooding on the urban areas in the Clarence Valley be reduced by increasing the storage capacity of floodplains?

In order to answer the research question, the following project approach is applied. Six areas were identified, based on a fieldvisit and an extensive preliminary study, to implement flood mitigation measures and assess existing flood defences. Part of these flood defences are the Swan Creek Floodgate and the reinforced concrete levee wall of Maclean, which will be investigated on their performance. A fully calibrated numerical floodmodel provides input for the hydrological analysis. The model represents the current situation in the Valley. Scenarios are created by applying topographic adjustments. The new scenarios are implemented into the numerical model and the effectiveness on flood mitigation in urban areas is assessed by comparing the results of a 5, 20 and 50 year Average Reccurance Interval flood event to the current situation during one of these flood events.

By making use of the proposed floodplains and improving the performance of existing flood defences, the flood defence system of the Clarence Valley can be extended. It can be concluded that it is possible to reduce the impact of flooding in the urban areas of the Clarence Valley by increasing the storage capacity of floodplains around Grafton. Therefore, the usage of a ’Room for the River’ strategy can be a solution to the problems the Clarence Valley is facing, and possibly might be applicable to more flooding-vulnerable areas in Australia.