Remote Sensing of Wave Overtopping on Dynamic Coastal Structures

Chris E Blenkinsopp,Ollie Foss,Tom E Baldock,Paul M Bayle,Stefan Schimmels,Luis P Almeida

doi:10.3390/rs14030513

Abstract

The development of coastal regions combined with rising sea levels is leading to an increasing risk of coastal flooding caused by wave overtopping of natural beaches and engineered coastal structures. Previous measurements of wave overtopping have been obtained for static coastal structures using fixed current meters and depth sensors or tanks. These are unsuitable for dynamically stable coastal protection structures however, because the geometry of these structures is expected to evolve under wave action. This study investigates the potential to use elevated 2D laser scanners (Lidar) to remotely sense the flow volumes overtopping the time-varying crest of a porous dynamic cobble berm revetment. Two different analysis methods were used to estimate the wave-by-wave overtopping volumes from measurements of the time-varying free surface elevation with good agreement. The results suggest that the commonly used EurOtop parameterisation can be used to estimate overtopping discharge to an acceptable precision. An advantage of the remote sensing approach reported here is that it enables the spatial distribution of overtopping discharge and infiltration rate to be measured. It was found that the overtopping discharge on a porous dynamic revetment decays rapidly landward of the structure crest, and that this has implications for safety and structure design.

Highlights

Continued population growth combined with sea-level rise and climate change-related increases in storm intensity are placing ever-greater stress on the coastal zone, leading to increased reliance on existing coastal protection structures or the installation of new defences
Due to the limitations of fixed instrumentation for measuring overtopping on a dynamic revetment it was not possible to validate the Lidar-based methodologies outlined in Section 2.2 against traditional overtopping measurement techniques
The results presented in this paper indicate that 2D scanning Lidar can be used to capture wave overtopping of porous dynamic coastal structures with evolving geometry

Summary

Introduction

Continued population growth combined with sea-level rise and climate change-related increases in storm intensity are placing ever-greater stress on the coastal zone, leading to increased reliance on existing coastal protection structures or the installation of new defences. Management of wave overtopping is a key criterion in the design of coastal protection structures, which must be designed to restrict overtopping to tolerable levels during design storm conditions. Historical design guidance has typically focussed on limiting time-averaged overtopping discharge to minimise coastal flood risk. Recent design guidance specifies acceptable limits on peak overtopping discharge for different structure types and safety considerations [2]. Wave overtopping of fixed coastal structures is typically measured using overtopping tanks which capture the flow volumes that pass over the structure crest in the laboratory [3,4,5]. Field measurement of wave overtopping using tanks has been undertaken but is limited to a relatively small number of studies [4,6,7]

Methods

Results

Conclusion