Analysis of workload required for removal of drifting pumice after a volcanic disaster as an aspect of a port business continuity plan: A case study of Kagoshima Port, Japan

This report discusses how for most major ports in Japan, a business continuity plan (Port-BCP) has been developed to cope with potential functional disorder in port operations caused by natural disasters. The objectives of a Port-BCP are to maintain the minimum vital activities, such as transportation of emergency supplies, under critical conditions, and to enable resumption of normal operations within a reasonable period. However, Japan's existing Port-BCP plans focus only on earthquake and/or tsunami disasters and do not consider volcanic events. This study assessed the impact of pumice fallout in the Kagoshima Port area following a supposed large-scale eruption of the adjacent volcano, Sakurajima.

To estimate the potential volume and mass of pumice deposited in Kagoshima Bay, numerical simulations were conducted using a tephra transport model with varying wind parameters. Based on the results, the duration of the work required to remove the deposited pumice from the port area and navigation channels was estimated. Then, analysis of tidal circulations under surface wind stress was conducted using a 3D ocean model to clarify the characteristics of the currents in Kagoshima Bay. On the basis of the calculations of both pumice fallout and tidal currents, the surface drift of the floating pumice was analyzed. The total mass of floating pumice, as the object for removal, is presumed to decrease with time. Therefore, the temporal variation of the total mass of floating pumice was investigated by considering several physical mechanisms.