Abstract
The interpretation of sediments deposited by prehistoric tropical cyclones (TC's) is limited by a lack of modernanalogues, particularly in the South Pacific. On 13 March 2015, TC Pam made landfall on Vanuatu, reaching Category 5 intensity with 10-minute sustained wind speeds as high as 270 km/h. Three months after landfall, we measured flow height (terrain elevation plus storm flow depth) and inland extent of TC Pam's maximum coastalinundation (composed of astronomical tides, storm surge, and superimposed storm waves), and described the sedimentological characteristics of the TC Pam overwash sediments from trenches and transects at two sites(Manuro and Port Resolution Bay).
At Manuro (a mixed-carbonate embayment), the maximum flow height was 5.29 m mean sea level (MSL),with an inland extent of 106 m. The TC Pam sediments transition from a coarse to medium grained (mean: 1.07F) carbonate sand (<= 10="" cm="" thick)="" to="" pumice=""><= 18="" cm="" thick)="" that="" extends="" 400="" m="" inland="" into="" lake="" otas.="" the="" tc="" pam="" overwash="" sediments="" are="" characterized="" by="" a="" coarsening="" upward="" sequence="" (1.45="" to="" 0.23="" phi)="" followed="" by="" a="" finer="" grained="" eolian="" cap.="" at="" port="" resolution="" bay="" (a="" volcaniclastic="" beach,="" prb),="" the="" maximum="" flow="" height="" was="" 3.30="" m="" msl="" (1.51="" m="" flow="" depth),="" with="" an="" inland="" extent="" of="" 117="" m.="" the="" tc="" pam="" overwash="" sediments="" transition="" from="" a="" medium="" grained="" (mean:="" 1.76="" phi)="" volcanic="" sand=""><= 44="" cm="" thick)="" to="" pumice=""><= 5="" cm="" thick)="" that="" extends="" 320="" m="" from="" the="" shoreline.="" a="" subtle="" fining="" upward="" sequence="" was="" present="" in="" trench="" prb2,="" whereas="" prb1,="" prb3,and="" prb4="" contained="" tc="" pam="" sediments="" that="" were="" laminated="" and="" showed="" little="" to="" no="" vertical="" gradation="" in="" grainsize.="" at="" prb,="" we="" applied="" an="" inverse="" sediment="" transport="" model="" to="" reconstruct="" maximum="" flow="" depths="" using="" laboratory="" derived="" settling="" velocities="" and="" the="" distance="" from="" the="" berm.="" the="" reconstructed="" flow="" depths="" at="" prb2(1.43="" m),="" prb3="" (1.36="" m),="" and="" prb4="" (1.34="" m)="" compare="" favorably="" with="" the="" observed="" estimate="" (1.51="" m),="" illustrating="" the="" applicability="" of="" the="" inverse="" sediment="" transport="" model="" to="" reconstruct="" flow="" depths="" of="" prehistoric="" landfalling="">