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Data-driven prediction of saltmarsh morphodynamics 10.17863/CAM.24102 Evans, Ben Richard 000000030643526X Möller, Iris 0000000319712932 Spencer, Thomas 0000000326106201 Saltmarshes provide a diverse range of ecosystem services and are protected under a number of international designations. Nevertheless they are generally declining in extent in the United Kingdom and North West Europe. The drivers of this decline are complex and poorly understood. When considering mitigation and management for future ecosystem service provision it will be important to understand why, where, and to what extent decline is likely to occur. Few studies have attempted to forecast saltmarsh morphodynamics at a system level over decadal time scales. There is no synthesis of existing knowledge available for specific site predictions nor is there a formalised framework for individual site assessment and management. This project evaluates the extent to which machine learning model approaches (boosted regression trees, neural networks and Bayesian networks) can facilitate synthesis of information and prediction of decadal-scale morphological tendencies of saltmarshes. Importantly, data-driven predictions are independent of the assumptions underlying physically-based models, and therefore offer an additional opportunity to crossvalidate between two paradigms. Marsh margins and interiors are both considered but are treated separately since they are regarded as being sensitive to different process suites. The study therefore identifies factors likely to control morphological trajectories and develops geospatial methodologies to derive proxy measures relating to controls or processes. These metrics are developed at a high spatial density in the order of tens of metres allowing for the resolution of fine-scale behavioural differences. Conventional statistical approaches, as have been previously adopted, are applied to the dataset to assess consistency with previous findings, with some agreement being found. The data are subsequently used to train and compare three types of machine learning model. Boosted regression trees outperform the other two methods in this context. The resulting models are able to explain more than 95% of the variance in marginal changes and 91% for internal dynamics. Models are selected based on validation performance and are then queried with realistic future scenarios which represent altered input conditions that may arise as a consequence of future environmental change. Responses to these scenarios are evaluated, suggesting system sensitivity to all scenarios tested and offering a high degree of spatial detail in responses. While mechanistic interpretation of some responses is challenging, process-based justifications are offered for many of the observed behaviours, providing confidence that the results are realistic. The work demonstrates a potentially powerful alternative (and complement) to current morphodynamic models that can be applied over large areas with relative ease, compared to numerical implementations. Powerful analyses with broad scope are now available to the field of coastal geomorphology through the combination of spatial data streams and machine learning. Such methods are shown to be of great potential value in support of applied management and monitoring interventions. University of Cambridge 2018-07-20 Thesis Doctoral Doctor of Philosophy (PhD) en European Commission FP7 Space project "Foreshore Assessment using Space Technology (FAST)" - Grant No. 607131 https://www.repository.cam.ac.uk/handle/1810/276823 https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/aa13a5b6-2eec-427a-9e38-0cc3728525dd/download 87eda9de84448d1f82354d60eee3eb5f https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/c5ab3fb3-14e7-4b41-ae48-a2375ee2e064/download e36b4cb6be671ff80fefd6c743db972e https://creativecommons.org/licenses/by-nc-sa/4.0/ Coastal wetland morphodynamics morphology modelling machine learning data mining data analytics remote sensing earth observation spatial statistics data-driven empirical spatial modelling salt marsh saltmarsh big data satellite image analysis coastal analytics environmental coastal protection risk prediction forecasting neural network boosted regression tree bayesian network