Changes in runup characteristics between swash and collision conditions

Changes in runup characteristics between swash and collision conditions: a Field Study

Dijkstra, Twan (TU Delft Civil Engineering and Geosciences)

de Vries, S. (graduation committee)
Tissier, M.F.S. (graduation committee)
van Wiechen, P.P.J. (mentor)
Rutten, J. (graduation committee)

Delft University of Technology

Civil Engineering

REALDUNE/REFLEX

2022-10-04

Estimating wave runup is of crucial importance during a coastal risk assessment. Currently, runup levels are usually calculated using empirical formula derived from experiments conducted at beaches all over the world, and during different beach states. During this research, conditions are analyzed where runup reaches the dune toe and above. The main objective of this research is to examine the changes in the runup characteristics, which are the wave setup, the infragravity swash motions (low frequency wave motion) and the incident swash motions (high frequency wave motion). In order to examine these conditions, a fieldwork experiment has be conducted at the Sand engine near Kijkduin (South Holland). a dune of 150 (m) in width and 5.5 (m) above NAP (Nieuw Amsterdams Peil) have be constructed near the waterline. Instruments have been installed which have monitored the incoming wave conditions and the behavior of the hydrodynamic conditions at the waterline. One of these instruments was an instrument new to measurements conducted at the coast. This was a LLC (Line scanning Low Cost) LiDAR, which was used to track the runup during extreme wave conditions.
The LLC LiDAR was evaluated in terms of measuring the nearshore hydrodynamics by comparing the water level measured by the LLC LiDAR to the water level measured by a pressure sensor. The water levels from both instruments compared well with an 𝑅2 ranging from 𝑅2 = −0.86. The match in the peaks of the water levels were lower, showing 𝑅2 in the range of 0.34 − 0.78.
Data from the Fieldwork Experiment showed an increase in incident swash wave height during collision conditions when compared to swash conditions. Although the nearshore wave field showed similar conditions between the swash and collision conditions, the swash height showed an increase. Several parameters have been investigated to find the dependence of runup height to the offshore wave or beach characteristics. A best fit is found between runup and the beach slope (𝑅2 = 0.86), also indicating that swash motions are significant. Runup heights during these conditions are also compared to an empirical runup formula. This comparison indicated that runup elevations could still be predicted during conditions where runup reaches above the dune toe elevation.

runup
SWASH
LiDAR

http://resolver.tudelft.nl/uuid:44c8cf8d-bb27-4e33-aa96-4d1de2889f2d

Student theses

master thesis

© 2022 Twan Dijkstra