Dynamics Of Surge Run-Up On Dry Bed

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)


Applied Marine Physics/Ocean Engineering


An understanding of the dynamics of the leading part of runup caused by storm surges or tsunami waves will provide valuable information for improving the safety of coastal construction and for determining the extent of coastal flooding. Laboratory experiments and a modified boundary layer theory are used to determine the velocity field, pressure field and frictional forces in the leading edge (front) of a surge as it runs over a dry beach. The simplified situation of a steady surge is considered as an approximation to surges which slowly change shape and speed in the process of run-up. A two dimensional model, which takes into account the effect of vertical velocities and accelerations, is derived. The non-hydrostatic pressure field is determined by a numerical finite element technique, using eddy viscosities determined by Prandtl's mixing length hypothesis. Concomitant experimental investigations with reduced scale surges verify the theory. It is shown that the pressure exceeds that of hydrostatic in the region close to the tip. In the leading front of a surge, variations of the bottom drag coefficient with Reynolds number are found to be similar to that of a rough pipe. Based on the present findings, a method is suggested to compute the surge profile. Further, applicability of this method to the computations of the shoreward boundary conditions in numerical tsunami flooding models is discussed. The investigations are also extended to surge forces on a structure, by computing the forces on a pile, using the Morison equation.


Engineering, Marine and Ocean

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