Ground-penetrating radar and sedimentological analysis of Holocene floodplains: insight from the Tuross valley, New South Wales

Ground-penetrating radar (GPR) has been used on an array of floodplain type s on the lower Tuross River, in southeastern New South Wales, as part of an investigation into controls on channel-floodplain relationships. Ground-pe netrating radar transects from two floodplains are presented, along with se dimentological detail from trenches dug along the profiles at key locations . Sedimentological investigations showed that 100 MHz antenna gave an appro ximation of overall bedding trends in the upper 3 m when automatic gain con trol processing was used. Spreading and exponential compensation processing provided insight into textural changes associated with increased silt cont ent distal of the levee crest. One trench showed that thinning beds were re sponsible for onlapping reflectors. Signal attenuation at similar to4 m dep th below the raised floodplain surface resulted from a >50 cm-thick bed of sandy clay. The close integration of GPR and sedimentological data produced an excellent dataset, that enabled form-process associations and floodplai n evolution to be established for these sandy floodplains. However, accurat e subsurface assessment and interpretation must stem from carefully combine d GPR and sedimentological datasets.