Floods in ideal landscapes follow a coherent pattern where single water-covered areas expand and afterward recede following the inverse sequence, but deviate in real landscapes due to natural or human factors resulting in water coverage shifts. Using remote sensing, we introduced two indices to describe the discrepancies between spatially integrated versus pixel-level frequency distributions under maximum inundated conditions (dext) and throughout all flooding conditions (dtot), expressed as the relative weight of shifts on each landscape's maximum registered coverage, theoretically ranging between no displacement (<20%) to maximum displacement (≪inf). Globally, over 36 years inundations exhibited redistributions representing, on average, 25% and 45% of their peak extents revealing previously unnoticed extra engaged areas and rotational movements within events, rising up to 500% in meandering rivers (South America) and irrigated croplands (Central Asia). We also assessed the influence of natural and human variables and discussed the indices' potential for advancing flood research. Plain Language Summary While in ideal landscapes surface water should display the same spatial distribution across the expansion and recession stages of any flooding event, real dynamics may drift away from this expected pattern. We developed two indices based on remote sensing data to locate where these shifts are important and understand how they are influenced by nature and humans. By analyzing data from around the world, we discovered that thanks to the displacement from the ideal distributions, surface water covered globally an extra quarter of the area. Natural factors like low terrain ruggedness and high aridity foster much larger inundation displacement. In regions hosting rivers that carry large quantities of sediment and often change their course (e.g., India and Perú), displacement engages five times more area in floods than expected. We also found that water infrastructure like reservoirs and irrigation also influenced inundation displacement. For instance, displacement was very relevant in intensely irrigated regions like Central Asia and Australia, reflecting surface water deviation as needed for crop production. Because these variations scope water's spatiotemporal dynamics with important implications for the provision of many ecosystem services, their quantification and assessment allow us to monitor and understand our ongoing imprint on regional inundation dynamics.
Torre Zaffaroni, P.; Houspanossian, J.; Di Bella, C. M. & Jobbágy, E. G. (2023). Space - time inconsistencies in the dynamics of water coverage : tracking walking floods. Geophysical Research Letters,50, (23),e2023GL105224
10.1029/2023GL105224
Torre Zaffaroni, Paula, Houspanossian, Javier, Di Bella, Carlos Marcelo, Jobbágy, Esteban G.. 2023. "Space - time inconsistencies in the dynamics of water coverage : tracking walking floods". Geophysical Research Letters 50, no.23:e2023GL105224.
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