Examinando por Autor "del Moral-Erencia, Jose D."
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Ítem Flood hazard mapping with distributed hydrological simulations and remote-sensed slackwater sediments in ungauged basins(MDPI, 2021-12-03) del Moral-Erencia, Jose D.; Bohorquez, Patricio; Jiménez-Ruíz, Pedro J.; Pérez-Latorre, Francisco J.We present a basin-scale method to assimilate hydrological data from remote-sensed flood evidence and map civil infrastructures with risk of flooding. As in many rural areas with a semi-arid climate, the studied catchments do not contain stream gauge, and precipitation data does not capture the spatial variability of extreme hydrological events. Remote-sensed flood evidence as slackwater sediments were available at the whole basin, allowing the paleohydrological reconstruction at many sites across the catchment. The agreement between the predicted and observed inundation area was excellent, with an error lower than 15% on average. In addition, the simulated elevations overlapped the observed values in the flooded areas, showing the accuracy of the method. The peak discharges that provoked floods recorded the spatial variability of the precipitation. The variation coefficients of the rainfall intensity were 30% and 40% in the two studied basins with a mean precipitation rate of 3.1 and 4.6 mm/h, respectively. The assumption of spatially uniform precipitation leads to a mean error of 20% in evaluating the local water discharges. Satellite-based rainfall underpredicted the accumulated precipitation by 30–85.5%. Elaborating an inventory of the civil infrastructures at risk was straightforward by comparing the water surface elevation and transport network. The reconstructed maps of rainfall rate were used in the distributed hydrological model IBERPLUS to this end. Recent flood events that overtopped the infrastructures at risk verified our predictions. The proposed research methods can be easily applied and tested in basins with similar physical characteristics around the Mediterranean region.Ítem The fascination of a shallow-water theory for the formation of megaflood-scale dunes and antidunes(Elsevier, 2019-04-12) Bohorquez, Patricio; Cañada-Pereira, Pablo; Jimenez-Ruiz, Pedro J.; del Moral-Erencia, Jose D.Exceptional megaflood-scale bedforms on Earth are commonly associated with the catastrophic draining of glacial lakes in the late Pleistocene. The widest studied events have been the Missoula and Altai floods with 300–700 m flow depth, 1–20 m bedform height and 10–300 m wavelength. Nowadays, the Saint-Venant equations have succeeded at simulating the catastrophic glacial-lake drainage process numerically, but we still lack a depth-averaged morphodynamic theory able to predict the growth of dunes and antidunes. The disparity of spatial scales in megafloods prevents the use of non-depth-averaged rotational flow equations, motivating the present shallow-water theory for the formation of megaflood-scale bedforms. We adopt a non-equilibrium sediment transport equation rooted in Einstein's pioneering work. Here we prove that the bed instability triggers to form dunes and antidunes simply by lagging the entrainment term for sediment mass conservation, or the bottom shear stress, with respect to the depth-averaged flow velocity. We formalise this result using a linear stability theory that captures the existence regions of dune and antidune in addition to the roll wave instability. Furthermore, in the spirit of Kennedy (Annu. Rev. Fluid Mech., vol. 1, 1969, pp. 147–168), we derive a closed-form solution of growth rate and wave speed of the bedform. The nondimensional groups controlling the linear instabilities are the Froude number, ℱr, the Shields parameter, Sh, and the grain roughness relative to flow depth, Subsequently, we simulate the drainage of the largest Missoula flood numerically to explain the formation of giant antidunes in the Camas Prairie (Montana, US) during the late stage of the megaflood. Also considered are large fields of gravel dunes in the Kuray-Chuja Lake Basin (Altai Mountains, Siberia). The simulated hydraulic conditions over bedforms in both basins yield values of the nondimensional parameters that lie in the theoretical region of dunes and antidunes according to the proposed theory and in situ measurements in sandy rivers and flume experiments.