Visualisation of flooding along an unvegetated, ephemeral river using Google Earth Engine: Implications for assessment of channel-floodplain dynamics in a time of rapid environmental change

Given rapid environmental change, the development of new, data-driven, interdisciplinary approaches is essential for improving assessment and management river systems, especially with respect to flooding. In world's extensive drylands, difficulties in obtaining field observations major hydrological events mean that remote sensing techniques are commonly used map floods assess flood impacts. Such techniques, however, dependent on available cloud-free imagery during or immediately after peak discharge, single images may omit important flood-related hydrogeomorphological events. Here, we combine multiple Landsat from Google Earth Engine (GEE) precipitation datasets high-resolution (<0.65 m) satellite visualise flooding associated channel-floodplain dynamics along a 25 km reach unvegetated, ephemeral Río Colorado, Bolivia. After cloud shadow removal, surface reflectance data were calculate Modified Normalized Difference Water Index (MNDWI) extents patterns. From 2004 through 2016, annual area narrow (<30 m), shallow (<1.7 fine-grained (dominantly silt/clay) channels was positively correlated (R2 = 0.83) 2-day maximum totals. Rapid meander bend migration, bank erosion, frequent overbank formation crevasse channels, splays, headward-eroding avulsion (shifting flow one channel another). These processes demonstrate ongoing, widespread despite low stream powers cohesive sediments. Application our study other dryland rivers will help generate comparative controls, rates, patterns timescales under scenarios climate change direct human impacts, potential implications improved management.