Flood reconstruction using botanical evidence in Rapentosa catchment, in Marathon, Greece

Περίληψη

Botanical evidence has been used in the past for flash flood analysis, especially when instrumental data were scarce. This work focuses on the use of such evidence as a tool to study flash flood phenomena in Rapentosa torrent, in Marathon, Greece. To this aim, impact scars induced during past flood events on trees along the torrent, were considered water stage indicators and were used to determine discharge magnitude of these flow episodes. Samples extracted from the scarred specimens with the aid of an increment borer, were used to date these impacts wounds. 1-D hydraulic modeling was used to provide a reconstruction of the highest-discharge event, while results were cross-examined with historical damages to verify the outcome of the analysis. Analysis showed a total of 22 impact wounds along the torrent indicating discharge values between 17.1 m3/s and 84.9 m3/s during past flow episodes. Three flash flood events were identified in 1996, 1998 and 2001. Hydraulic modeling of the 2001 event, which presented the highest flow values, illustrated its extent and water depth across the floodplain, presenting good correlation with the available documentary evidence.