Observations and Modeling of Coastal Boulder Transport and Loading During Super Typhoon Haiyan

Abstract

Boulders numbering in the high hundreds/low thousands, and with masses up to ∼ 30 tonnes, were transported onshore by Super Typhoon Haiyan in Calicoan Island, Philippines to maximum ground elevations that could exceed 9 m and terminal positions up to ∼ 180 m inland. One-dimensional Boussinesq hindcasts of coastal boulder motion showed intermittent transport initiated at the fronts of infragravity swash bores. Transport distances were found to be highly sensitive to wave-height, enough so that observations of terminal positions may be a viable method of estimating rough paleostorm magnitudes. The large accelerations at bore fronts generated significant inertial forces, particularly for larger boulders, but drag forces had greater root-mean-square magnitudes in all simulations. Widely used relations to infer fluid velocities from boulder properties were tested using modeled boulders -inferred velocities at modeled terminal boulder positions were compared to maximum computed Boussinesq fluid velocities at these locations and found A. B. Kennedy et al.to be significantly lower. This underprediction of inferred velocities was greatest for smaller boulders that were strongly mobile. Inferred drag loads compared to modeled values were somewhat more accurate for large boulders when a Froude number of unity was assumed to estimate flow depths. Although these boulders were unequivocally transported by storm waves, their large sizes and distances traveled venture into what has been considered the tsunami range. Thus, care must be taken to interpret the provenance of coastal boulder fields with unknown origin for lower to mid-latitude regions.

Study on Locally Varying Inundation Characteristics Induced by Super Typhoon Haiyan. Part 1: Dynamic Behavior of Storm Surge and Waves Around San Pedro Bay

“…Discussions and investigations of more detailed inundation characteristics along the east coast of Eastern Samar are presented in several papers [e.g. Gunasekara et al, 2014;Shimozono et al, 2015;Kennedy et al, 2016; and the Part 2 of the present study, Tajima et al, 2016]. While inundation characteristics are dominantly determined by storm waves along the east coast of Eastern Samar, storm surge appears to reasonably represent the observed inundation heights around the inner part of San Pedro Bay where the city of Tacloban is located.…”

Study on Locally Varying Inundation Characteristics Induced by Super Typhoon Haiyan. Part 2: Deformation of Storm Waves on the Beach with Fringing Reef Along the East Coast of Eastern Samar

“…Kennedy et al [2015] found a number of boulders with estimated masses up to 30 tonnes transported onshore by Haiyan around the south part of Calicoan islands located at the south end of the east coast of Eastern Samar. Shimozono et al [2015] pointed out that the observed runup heights locally vary along the nearly straight coast line of Eastern Samar and suggested that observed runup heights and the width of fringing reef show positive correlations.…”

Modeling boulder transport by coastal waves on cliff topography: Case study at Hachijo Island, Japan

“…Vertical inertia coefficient (C My ) 2.5 Wilson and Reid (1963) defined an inertia coefficient of 3.29 for calculating the inertia force acting on a pipeline located on the sea floor. Kennedy et al (2016) and Imamura et al (2008) respectively determined inertia coefficient as 2.5 and 1.67 for their proposed boulder transport formulation. In this way, the appropriate value of inertia coefficient is not reasonably defined.…”

“…In this study, we calculated the empirical equation using data from the laboratory experiment in Malavasi et al (2007) coefficients is difficult and their values have considerable uncertainty. For these reasons, we conducted a sensitivity analysis of the coefficients using the method of Kennedy et al (2016) to reveal the range of possible. We changed the coefficients as shown in Equation (20) using a random number R(-) with a range of [0-1].…”

“…where μ s is the coefficient of static friction. Kennedy et al (2016) performed 400 simulations for the sensitivity analysis of 8 parameters (6 coefficients used in the equations, waveform of storm wave, and dimension of boulder). In our simulation, we also gave 400 simulations for the sensitivity analysis by changing 7 coefficients using random numbers as shown in Table I.…”