Quantifying flow conditions during extreme coastal events from deposits

Extreme coastal event leave behind sediments that can be employed to learn about the causative process. Fortunately, these extreme coastal events do not occur frequently enough to only rely on past few decades. Therefore, the geologic record needs to be interrogated. Different different extreme events can be the driver of significant impact and coastal change. Learning about the different causative processes from their geologic record is important because they can occur in the same geographic region. Respective event histories and magnitudes need to be inferred from the geologic record in order to support meaningful and robust quantitative data for respective hazard assessments. Inferring the flow conditions during extreme coastal events does not come without problems. The preservation potential and post-depositional changes impact what is transferred from the original deposits into the geologic record. One can pretty much assume that an event deposit in the geologic record is not complete. Furthermore, for inversion, a small, but nonetheless important, amount of information about the pre-transport conditions are needed. The assumed incompleteness, unknown pre-transport conditions, and simplifications of the flow and sedimentation model result into a number of assumptions that makes it necessary to quantitatively address the impact of the assumptions on the inverted flow conditions of extreme coastal events. In a deterministic framework, these assumptions would lead to results of very limited robustness. However, we will show how when moving into a probabilistic framework the results become more useful and intuitive because some of the assumption can be addressed as distribution and go into a general quantification of uncertainty. We will show results for boulder deposits as well as sand.