04 affidabilita modelli_per colata_en
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A debris flow occurs when high intensity rainfall rapidly produces runoff that entrains debris material in channels. This forms a solid-liquid wave that increases in velocity as it erodes sediment while flowing downstream. Eventually the debris flow slows and deposition begins. Accurately simulating debris flows requires models for rainfall-runoff hydrology, debris flow triggering, and downstream hydraulic routing that reproduce physical processes and are validated against measurements of past events. The reliability of simulation results depends on models' abilities to replicate measured quantities like discharge, erosion depths, deposition depths, maximum levels, and routing times.
04 affidabilita modelli_per colata_en
- 1. Carlo Gregoretti25/5/2017 Mekelle University - Debris Flows Capability and reliability of models for reproducing the physical processes associated to debris flows phenomena
- 2. Carlo Gregoretti25/5/2017 Mekelle University - Debris Flows Schematic 2D view of a debris flow event occurrence and development Deposition Debris flows commonly occur in channels draining small steep rock basins located in the upper part of the slopes where high intensity, short duration rainfalls, rapidly generate high runoff discharges , that are able to entrain large debris material laying at the bottom of channel, forming a solid-liquid wave RUNOFF Firehose effect debris flow triggering Formation of an immature debris flow Debris flow increases its velocity and erodes sediment s laying on the bed Formation of a mature debris flow with sediment sorting along the profile Debris flow slows and sediment deposition starts Rock cliffs Scree sediment
- 3. Carlo Gregoretti25/5/2017 Mekelle University - Debris Flows Schematic 3D view of a debris flow event occurrence and development Initiation area Transport area deposition area Debris material availability Very high slopes Abundant runoff
- 4. Carlo Gregoretti25/5/2017 Mekelle University - Debris Flows In brief, a debris flow results from three different physical processes 1. Abundant runoff production after high intensity precipitation 2. Entrainment of debris material laying on the bottom of channels with formation of a solid-liquid wave 3. Downstream routing of the solid-liquid wave We need three different models for debris flow simulations: 1. Hydrologic model (Rainfall-Runoff) for rocky headwater basins 2. Triggering model for determining the solid-liquid hydrograph 3. Hydraulic model for downstream routing Physical processes associated to debris flow
- 5. Carlo Gregoretti25/5/2017 Mekelle University - Debris Flows Reliability of the results of a simulation, mainly depends, on model capabilities of reproducing measured quantities (discharge, erosion and deposition depths, maximum reached levels, routing times) of past-occurred events. Hydrological models should be tested against discharge measurements taken as close as possible to the feet of rocky cliffs. Hydraulic models should be tested by comparing simulated and measured/estimated erosion and depositon depths, as well as the maximum levels reached by the mixture free surface and routing times. Hydraulic models that do not directly simulate erosion and deposition should not be considered. Models have to be tested