Analysis of Model Performance Related to Uncertainty in the Model BEACHPLAN for the Simulation of Shoreline Evolution

Analysis of Model Performance Related to Uncertainty in the Model BEACHPLAN for the Simulation of Shoreline Evolution

Qiu, L.

Stive, M.J.F. (mentor)

Civil Engineering and Geosciences

Hydraulic Engineering

CoMEM Programme

2013-06-26

As a useful tool in understanding the coastal behaviours, one-line models , which are designed to simulate the long-term shoreline evolution in response to imposed wave conditions, coastal structures, and other engineering activities such as beach nourishment, have been developed and applied to a wide range of projects in coastal engineering and management. However, most of them are deterministic and not probabilistic, the model performance is associated with presumed uncertainty due to the high quality input data required and the large number of processes involved in reality but which are simplified in the one-line theory. In the past, the assessment of model performance has usually been a subjective judgement of goodness of fit, which depends on researchers’ expertise and experience by comparing prediction with observation. This dissertation study aims to find a method of evaluating the performance of one-line models such as BEACHPLAN, so as to qualify the model accuracy in an objective way. To measure the skill of a model, uncertainty, optimization and sensitivity modelling of beach behaviour related parameters, such as shoreline orientation, wave climates, etc., are investigated, which provide acknowledge of shoreline response to variable input data. Four error analysis methods: correlation, shoreline movement, probabilistic and distortion length, are employed to quantify the model errors. Applied to a set of proposed criteria-Model Performance Rating System (MPRS), error indicators of these four approaches are ranked so that the best-fit input parameter/model performance can be identified. The adapted assessment method is tested on a ‘‘log-spiral’’ shaped shoreline of Poole Bay, UK. Additionally, shoreline orientation is addressed in this dissertation study, which is critical in shoreline evolution analysis. The results show that the methods are able to evaluate the model performance and select the best match. The significance of the method adapted in this research is quantifying and reducing the model uncertainty and establishing model reliability. In the future, more validations with other numerical models are needed before it can be recognized as a sophisticated assessment method.

uncertainty
model performance
assessment
shoreline evolution
one-line model

http://resolver.tudelft.nl/uuid:fd708b26-f51a-4179-9724-1bb37e7d6bd7

Student theses

master thesis

(c) 2013 Qiu, L.