The design of multi-value sand nourishments

Relative sea level rise and climate change, but also the migration of the growing world population to the coast, continuously increase the pressure on the coastal system. In combination with the increased awareness for sustainability, the interests in the coastal zone become integrated and complex. Integrated Coastal ZoneManagement (ICZM) becomes increasingly important to satisfy the diverse societal needs in the coastal zone. Along sandy shorelines multi-value sand nourishments are therefore potentially valuable and feasible solutions. An example of amulti-value sand nourishment is the Sand Engine in theNetherlands. This innovative 21.5Mm3 mega nourishment was developed in line with the Building with Nature (BwN) design philosophy. To create value with multi-value sand nourishments for other endangered coastal zones in the world, a design methodology for multi-value sand nourishments is necessary. In this research a design methodology is developed that integrates the socioeconomic environment in order to design sand nourishments for the societal needs and determine their feasibility. To create optimal values for society with sand nourishments, the physical and the socioeconomic environments are integrated in the design cycle. The physical environments of sandy shorelines provide functions, and the desired values depend on the socioeconomic environment. To create an overview of the potential values of sandy shorelines, functions categories are defined: culture, economy, food resources, infrastructure, nature, safety, tourism & recreation and water resources. Sand nourishments aim to increase the functionality of sandy shorelines for one (or more) of these categories. In the developed methodology, the physical and the socioeconomic environment are integrated in the design cycle by quantifying the sandy shoreline function categories with indicators. In this way the functionality of the physical environment is translated to potential values for the socioeconomic environment and the societal needs are translated to benchmarked indicators for the physical environment. An application to Gold Coast’s Palm Beach in Australia illustrated that the developed methodology supports the design of multi-value sand nourishments. The most potential solutions for Palm Beach are assessed based on their feasibility in terms of finance and stakeholder commitment. At strategic level, the most potential was allocated to the solution to increase the sand buffer. At conceptual level, the concentrated nourishment was considered to be supported the most by the government and the businesses. An increased surf quality for experienced surfing, and therefore increased value for tourism & recreation of Palm Beach and the Gold Coast can be created with this solution.Hydraulic EngineeringHydraulic EngineeringCivil Engineering and Geoscience

The Durban Dig-Out Port, Project Durban

The Port of Durban is South Africa's premier port and hub of the region, especially for the Johannesburg (Gauteng Province) area. The current port will eventually not be sufficient to handle the capacity demand. The focus is on the development of a new port in the direct surroundings of Durban. A suitable new location is found at the old international airport. The Durban Dig-out Port is designed to cover a yearly container throughput of 10,000,000 TEU, a yearly liquid bulk throughput of 5,000,000 kL and 300,000 vehicles throughput per year. The governing vessel for the design is a 22,000 TEU container vessel with a length of 430 m, a width of 43.4 m and a draft of 16.3 m. The choice for the 22,000 TEU design vessel is reviewed. Based on global developments in ship manufacturing and a brief look at the developments in South Africa's container trade it is concluded that the 22,000 TEU vessel is recommended for the design of the port. In the proposed port layout the entrance channel is aligned such that it gives possibilities to bring the Isipingo estuary and its protected mangroves back to life. New land becomes available for an extension of the mangrove area and a new natural equilibrium between fresh and salt water inflow can be developed. The direction of the entrance channel also results in the central location of the turning circle and therefore the basins are relatively short. This makes manoeuvring for the vessels in the port convenient. A slight bend in the entrance channel is proposed to mitigate the wave action in the port. A straight entrance channel would lead to large downtime and has a direct impact on the port efficiency. The southern swell waves cannot enter the port due to the breakwaters and the eastern wind waves are either absorbed at the inside of the southern breakwater or at the safety beach at the end of the turning circle. The proposed sand bypass system makes sure that the coastal evolution is sustainable. In the proposed layout two configurations for the breakwaters are distinguished in terms of orientation and length. The proposed breakwaters are based on either a relatively high (10 kn) or low (6 kn) maximum vessel entrance speed. From research with a simplified wave model it is concluded that the shorter breakwaters cause downtime for the liquid bulk terminal during storm conditions from the south. During normal conditions it is however found that the liquid bulk terminal can be operational for more than 99% of the time. Next to that, it is found from the design of the breakwaters' cross sections that the breakwater dimensions become significantly larger at greater depths. However both breakwaters are found stable with numerical stability analysis and in combination with the result of the wave model it is concluded that the shorter configuration is preferred. This leads to significantly lower construction costs and the downtime of the liquid bulk terminal is limited.Civil Engineering and Geoscience

A biophysical model for seedling establishment in mangrove forests

Mangrove seedling establishment is crucial to the long-term development of mangrove forests. This study incorporates a process-based approach for seedling establishment in a process-based hydrodynamic model. The biophysical model is used to simulate seedling establishment in the Firth of Thames estuary (New Zealand). The results are compared to a random seedling establishment approach that has been often-used in long-term mangrove forest development models. While small differences were observed in terms of the seaward extent of seedling establishment, larger differences were found for the patchiness and density of the establishing seedlings. The results of the process-based approach showed a more localized pattern of seedling establishment, in line with field observations in the Firth of Thames. This pattern was opposed to the more spatially uniform establishment patterns predicted with the random establishment approach. These differences reveal that the implemented seedling establishment approach may affect long-term mangrove forest development models. Moreover, the process-based approach is more easily setup and calibrated with physical parameters that can be measured in the field