The historic inner-cities in The Netherlands are largely known for their iconic channels and their accompanying quay walls, of which a significant number were constructed over 100 years ago. Due to the limited available space in the sub-surface of the urban environment, a high number of utility lines (i.e. potable water pipes and sewer systems) are situated in the vicinity of these quay walls. In recent years, a number of quay wall collapses have occured in the inner-city of Amsterdam, some of which have been attributed to utility line leakages. However, research into the interaction between inner-city quay walls and utility lines is lacking. Thus, the aim of this report is to answer the following question: "How does utility line leakage relate to deformation and failure of Amsterdam's inner-city quay walls and when does this interaction become significant?". The interaction between utility lines and inner-city quay walls works in both ways, thus the research is split up accordingly. The effects of utility line leakages on quay wall displacement and failure were qualitative studied using a literature study. The effects of quay wall displacement on utility line leakages were quantitatively studied using an analytical model. In this model, the interaction between utility line and surrounding soil was represented using a beam on a Winkler foundation, i.e. a beam supported by a distributed spring. The stiffness of the spring was represented as bi-linear, resulting from the equilibrium bearing capacity of the soil. Quay wall displacements ranging from 20 up to 100 mm were applied to the most common types and outer diameters of utility lines found in the vicinity of quay walls. Utility line leakage is deemed to occur if a predetermined threshold is passed of either maximum angular deflection, maximum allowable bending moment or maximum allowable shear force, each resulting from the utility line displacement. Although the scope of the study is the inner-city of Amsterdam, the study can be used in other cities with inner-city quay walls, given the circumstances are similar. The literature study showed that quay wall displacement and failure due to utility line leakage follows from internal erosion processes. Two requirements have to be met for instigation of internal erosion: a local head difference between the water level in the channel and the groundwater level in the soil body behind the quay wall, and an open connection in the quay wall structure in the vicinity of the aforementioned local head difference, enabling the flow of soil via water. The rise of the groundwater level can be the result of a potable water pipe leakage, but can also follow from external factors like heavy rainfall. Three forms of open connections were appointed. The first is scour protection screen leakage, which can result in erosion underneath the structure. The second is quay wall floor leakage, which can result in both erosion underneath structure and erosion in the soil body behind the quay wall. The third is sewer leakage, which can result in erosion in the soil body behind the quay wall. In the latter, the aforementioned head difference is not required. This is because the direction of groundwater flow is not towards the channel, but towards the sewer leakage, given that the sewer pipe is located below the groundwater level. Erosion underneath the quay wall floor can result in quay wall displacement towards the channel, while erosion in the soil body behind the structure can result in the formation of a subsidence pit. Both erosion underneath- as well as behind the structure can result in (further) deformations of utility lines. The former through quay wall displacement towards the channel, resulting in local soil displacement in which said utility line is embedded in. The latter trough local loss of soil, resulting in a local reduction of support. Both have the potential to result in relative utility line displacements, which can result in leakages. This process is can be denoted as a positive feedback loop. Actual failure of the quay wall due to utility line leakage can come in the form of collapse of the quay wall towards the channel or collapse of the road on top of the structure in the formed subsidence pit. Due to the dependence on external factors, quay wall failure resulting from utility line leakage can be described as a second order effect. It was found that exceedance of the maximum allowable angular deflection of the utility line joints is most likely to result in leakages. Leakage due to exceedance of maximum allowable bending moment is relatively less likely but still significant, while leakage due to exceedance of maximum allowable shear force is unlikely. In all utility lines, a higher bending stiffness resulted in a lower susceptibility to leakage. If utility lines are deemed susceptible to leakage, it is advised that these are monitored intensely.

The United States Army Corps of Engineers (USACE) is scheduled to present their solution for a storm surge barrier on Galveston Island in 2021 to congress for approval. A solution for an engineered dune system on the Galveston Island West End has been proposed, but storm surge models have shown that protection from this engineered dune only goes so far, moreover the search for a proper alternative that fulfills technical requirements and social political influences have proven to be challenging. This study aimsto assess different dune alternatives, proposed in different reports, with a range of multi disciplinary criteria. The assessment of dune alternatives will also result in guidelines that should be considered for design, maintenance and governance aspects for an engineered dune barrier on Galveston Island, TX. Using a multi disciplinary approach for the evaluation of the different dune alternatives, the following research question was formulated: To what extent do the various dune alternatives fit the requirements for a land barrier at the West End of Galveston Island, looking at both technical and sociopolitical aspects? In this context, technical requirements are defined as the storm surge-and rainfall coping capacities of the dune, i.e. against what kind of storm is the dune resistant. Social political influences are a combination of the perception by local residents that are directly influenced by the construction of a dune system, governmental forms of collaboration, and in provide an analysis of the maintainability of the dune alternatives using the storm surge capacities. The different dune alternatives that have been assessed consist of the dune system proposed by the USACE and GLO (2018), the big dune system proposed by Galvez (2019) and the hybrid dune system as proposed by Muller (2017) and will hereafter be called alternative 1, 2 and 3 respectively. In this report a fourth alternative was introduced which is based on the hybrid dune system by Muller (2017) and consists of a clay core instead of a concrete core. Alternative 4 was chosen in order to simulate the difference between a concrete core and a clay core. Based on XBeach calculations, the storm surge coping capability of each dune was determined by projecting 10 year-, 50 year- and 100 year storms onto the dune alternatives. ArcGIS maps from the Galveston Island allowed for projection of flow patterns on the island in order to determine the rainfall coping capacity. An evaluation of sociopolitical aspects was based on a review of the literature on dune systems, forms of collaboration between governmental and private entities, and interviews with various respondents consisting of private individuals and companies, as well as governmental agencies involved in the process. Analysis of the various dune alternatives, based on multi disciplinary criteria, demonstrated that alternative 1 is completely flattened in 50 year storm events, whereas alternatives 2, 3 and 4 show a good storm surge capacity. All alternatives aggravate the current rainfall capacity at Galveston Island West End, because each dune system poses an obstruction that is not there currently. Alternatives 2 through 4 show a good enough storm resilience, requiring post-storm recovery maintenance while still providing a reduced but fair storm surge capacity. The sociopolitical results indicate that Galveston Island West End residents wishes are only safeguarded for alternative 1. On this basis, the main recommendations are to perform tests upon the dune system alternatives regarding storm events occurring in succession, which is not unusual in the Gulf of Mexico. A combination of alongshore erosion rates from the Galveston Island and the effect of dune vegetation should be determined for the dune alternatives, since these aspects were not considered in this research. Further research is needed to identify the combined effects of rainfall and storm surge in order to get insights into the performances of a certain alternatives. Furthermore, the exact role including the desired storm surge capability should be well defined in order to determine which stakeholder wishes and influences are to be fully considered for the dune system design.