Modeling Catastrophic Flood Events in Osuga Valles, Mars using HEC-RAS

Osuga Valles is centered at approximately 14°50'S and 37°25'W just southeast of Valles Marineris. It is one of several catastrophic flood channels on Mars that emanates from a source region of surface collapse containing down-dropped blocks of material called 'chaotic terrain.' Surface flow features in Osuga provide evidence for enormous volumes of groundwater flowing out from the source collapse areas and subsequently eroding the channel downstream. Unlike most catastrophic flood channels on Mars, Osuga Valles terminates in a region of collapse as well.

Osuga Valles contains enormous channel bedforms, such as streamlined islands and grooves, and forms both singular and anastomosing channel segments and a cataract downstream as it empties into its terminal collapse region. We are interested in understanding the history of flooding in this system and will use HECRAS to generate a 2D model of catastrophic flows. We will use HRSC DTMs and MOLA tracks to determine channel cross-sections. We assume that the current morphology is the original morphology that existed during the time of catastrophic discharges. The model adjusts for the gravity on Mars. High water marks are taken at several cross-sectional profiles along MOLA tracks and are used as a reference elevation for the maximum discharge to flow through the channel. However, the unique characteristics of the channel geometry indicate multiple flood events from two source regions with the most recent stemming from the southern source collapse region and relatively older events produced from the source region to the north. The volumes of discharge can provide implications for the characterization of the subsurface and the hydrology of Mars.