STELAR-S2S

2013 fieldwork

During 2013 the STELAR-S2S team undertook two periods of intensive fieldwork during September and then again towards the end of October and into November. These campaigns were timed to coincide with the peak (September) and falling limb (October-November) of the annual monsoonal flood on the Mekong. The team conducted surveys at 11 sites (see image below) with a focus on obtaining high-resolution surveys of the bed and banks using Multi-Beam Echo Sounders (MBES) and Terrestrial Laser Scanning (TLS), detailed flow dynamics data from acoustic Dopple current profilers (aDcp), suspended sediment data to constrain sediment fluxes through each site and bathymetric data for the entire study reach using Single-Beam Echo Sounding (SBES).

Location of the 11 study sites visited in September and October 2013.

Collecting data during September and October 2013.

The team enjoyed every minute on the Mekong.

During the Septemeber field campaign, the team were joined by two undergraduate Royal Geographical Society fieldwork apprentices, Eleanore Heasley and Richard Campion who helped the team with data collection. Whilst the team were out in September, they experienced a typhoon-induced rapid rise in water levels. As Typhoons Usagi and Wutip passed over the northern part of the Mekong catchment, discharge began to rise from ~24000 m3/s when the team arrived, to ~60000 m3/s in a matter of days. Such a rapid rise may have had marked impact on bank erosion rates and levels of floodplain sedimentation. The fact that the team were there to record the rise and the processes operating on the river during the period means the STELAR-S2S team are in a fantastic position to explore the way large rivers behave during rapid-rise flood events.

Repeat surveys were undertaken during October-November 2013. Water levels were considerably lower (discharge ~20000 m3/s) than during September, meaning large swathes of river bank were exposed allowing the team to deploy the TLS to obtain high-resolution topography of the exposed banks. This data will be used to estimate the roughness of the river banks and to explore the relationships between bank roughness, near-bank flow structures and processes of bank erosion. In addition, many of these banks were captured whilst submerged in September with MBES. By comparing the October-November TLS data to the September MBES data, the team are in a position to assess the impact large floods have on bank morphology and assess any changes which occured associated with the passage of Typhoons Usagi and Wutip.