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This is the second part of a work describing hazard mapping for hydrogeological risk estimation

This is the second part of a work describing hazard mapping for hydrogeological risk estimation

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Danube floodrisk ii Danube floodrisk ii Presentation Transcript

  • About the Guidelines for Hazard Mapping Riccardo Rigon, Silvia Franceschi, Giuseppina Monacelli, Giuseppe Formetta Segantini - Mezzogiorno sulle Alpi Danube FloodRisk Project, Trento, September 26, 2012Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Credits of This Research Besides, being completed under the Danube Flood Risk EU Project is based on studies developed during the IRASMOS EU project and during a conjoint work with the “Servizio Bacini Montani” of the Autonomous Province of Trento 2 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Credits for these Slides Most of the slides picture were produced during pilot studies by: Hydrologis - ing. Silvia Franceschi, dr. ing. Andrea Antonello ingTerritorio - ing Christian Tiso and dott. geol. Alessandro Sperandio Mountainain-eering - dr. ing Silvia Simoni, ing. Fabrizio Zanotti, dr. ing. Matteo Dall’Amico Research used is much derived from common work with dr. ing Silvia Simoni and dr. ing. Cristiano Lanni who I thanks and acknowledge all. 3 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 This presentation the last year presentation, and related material can be found at: http://abouthydrology. blogspot.com search the blog for landslide triggering 4 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 3-4 October 2011 Low 5 Riccardo RigonMonday, October 1, 12
  • Danube Flood Risk Conference - Trento 3-4 October 2011 Preliminary Analisys Low 5 Riccardo RigonMonday, October 1, 12
  • Danube Flood Risk Conference - Trento 3-4 October 2011 Preliminary Analisys High Low Potential Risk In the average Low 5 Riccardo RigonMonday, October 1, 12
  • Danube Flood Risk Conference - Trento 3-4 October 2011 Preliminary Analisys High Low Potential Risk In the average Further Assessment considering uncertainties High Low 5 Riccardo RigonMonday, October 1, 12
  • Danube Flood Risk Conference - Trento 3-4 October 2011 Low Indicative analysis 6 Riccardo RigonMonday, October 1, 12
  • Danube Flood Risk Conference - Trento 3-4 October 2011 High Medium-Low Low Detailed analysis Simplified analysis Geological Analysis Geological Analysis Hydrological analysis Hydrological analysis Indicative analysis Simplified Hydraulic Hydraulic analysis analysis 6 Riccardo RigonMonday, October 1, 12
  • Danube Flood Risk Conference - Trento 3-4 October 2011 High Medium-Low Low Detailed analysis Simplified analysis Geological Analysis Geological Analysis Hydrological analysis Hydrological analysis Indicative analysis Simplified Hydraulic Hydraulic analysis analysis Comparison with other hazard maps 6 Riccardo RigonMonday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Steps in this presentation Preliminary Analysis Geology, Simplified Hydrology and (no) Hydraulics Hazard Maps 7 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Tools behind Field Survey, Data Collection, Maps analysis Geological techniques , Hydrological models, Hydraulic models GIS tools 8 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Summary of the Procedure Preliminary Analysis I. Geomorfological description of the Basin II. Data Review III. Historic Data Collection 9 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Summary of the Procedure Analysis I. Geological Analysis (orthophotos, existing cartography, field survey, geomorphological analysis, geophysical analysis, geotechnical analysis) II. Estimation of available sediment III. Hydrological analysis and models’ choice 10 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Preliminary Analysis La caccia al pericolo 11 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Basin Classification Rio Corda •Basin Area: 13.4 km2 •Min elevation: 924 m •Max Elevation: 2890 m •Mean slope .... •Two networks, torrents Courtesy of Mountain-eering 12 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Basin Classification Cismon - Canali Courtesy of Hydrologis 13 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Basin Classification Cismon - Canali WorldWind4JGrass - 14 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Data Inventory Cismon - DEM eith the main hydrography I would suggest in a map like this to indicate also some relevant points as peaks, etc. 15 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Data Inventory Canali - Idrografia P.A.T Hydrography can be improved by using Strahler ordering 16 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Data Inventory Orhophoto By itself the ortophoto is not very informative if other information is not superimposed 17 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Data Inventory Technical Map rio Corda 18 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Data Inventory Val di Casa - Land Cover From PAT 2003. 19 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 This is Land Cover grass, in this case 20 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 This is land use grazing, in this case 21 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Data Inventory Rio Corda - Geological Maps 22 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Data Inventory Summary DTM Hydrography Orthophoto Technical Maps Land Cover- Land Use Carta Geological Maps Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Data Inventory Historical data This landslide was referred in March 2003 from Servizio di Sistemazione Montana. The landslide involves a surface of 15500 m2 and cover around 100m of elevation, from the channel bed to ca. 1653 m a.s.l. Franceschini, 2003 24 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Data Inventory Historical data The depth of the movable sediment has been estimated to be around 10 m. The material of the landslide is made by clasts and boulder of sand matrix which often turn into limestone. Franceschini, 2003 25 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Going a little Deeper 26 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Data Inventory Missing data a little of survey can help. This is Val di Casa Past Events: 1. Flooding 1906 (missing source) 2. looding1987 (missinf source) In both the case the sediment that arrived to Carderzone was between 30.000 and 40.000 cubic meters This levee was realized in 1908 after the flood of 1906 27 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Analysis Always cite the source ! Sinthesis- Val di Casa In Val di Casa catchments are present five main lithological typologies: 1. Granite, granodiorite and tonalite Adamello 2. Mica schists, phyllites and paragneiss 3. lakes and rivers; 4. moraines coarse 5. detritus deposits with gravel prevalent; 28 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Analysis Sinthesis- Val di Casa Identification of the quaternary cover, in the low part of the basin with the use of orthophoto relative to different years: from left to right 2006, 2000, superposition of geology to the 2006 ortophoto. 29 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Analysis Di sintesi - Val di Casa Same as previous slide for the upper part of the basin: 2000, 2006 ortophotos, superimposition of geology tho 2006 orthophoto 30 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Analysis Lidar Data - Val di Casa Using LIDAR maps a good geologist is able to give an estimate of quaternary covers. 31 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Analysis Can be made a little more specific with a little of field survey - Case Cismon Cismon catchment is composed by two main geostructural domains: • the dolomitic domain (oriental): which is the Pale i S. Martino Area • the metamorphic domain (western): the area of mount Tognola. The river network developed close to the fault line. 32 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Analysis Can be made a little more specific with a little of field survey - Case Cismon Litostratigraphy of Cismon torrent. 33 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Analysis Can be made a little more specific with a little of field survey - Case Cismon Quaternary Formations 34 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Analysis Can be made a little more specific with a little of field survey - Case Cismon Landsliding: on the left the landslide at Pian delle Sfelde and at the right the deep landslide of Mount Tognola 35 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Analysis in the field GPS mapping (in yellow) of the first surveys on the basin 36 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Analysis in the field Three dimensional view of the survey with georeferencing of the photos. 37 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Analysis in the field 38 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological survey geophysics - rio Corda Objective: Give information about: • soil depth in some points (gray rectangles); • water table positions and main directions of subsurface flows; • stratigraphy and lithology. 39 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological survey geophysics - rio Corda Objective: Give information about: • soil depth in some points (gray rectangles); • water table positions and main directions of subsurface flows; • stratigraphy and lithology. 39 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological survey geophysics - rio Corda 39 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological survey geophysics - rio Corda Where to do the survey • area close to the head water and where there were landslides; • springs (light blue rectangles); • confluences of channels. 40 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological survey geophysics - rio Corda Where to do the survey • area close to the head water and where there were landslides; • springs (light blue rectangles); • confluences of channels. 40 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological survey geophysics - rio Corda 40 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Survey Geomechanics - rio Corda Objectives We want to know: • soil texture i.e. the fraction of sand, silt and clay; • the particle size of sediment in the bed of the torrents ; • strength parameters of soils (as proven in the lab); • hydrological parameters in situ hydraulci conductivity, residual water content, and porosity. 41 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Survey Geomechanics - rio Corda Objectives We want to know: • soil texture i.e. the fraction of sand, silt and clay; • the particle size of sediment in the bed of the torrents ; • strength parameters of soils (as proven in the lab); • hydrological parameters in situ hydraulci conductivity, residual water content, and porosity. 41 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Survey Geomechanics - rio Corda Where (red circles) • slopes prone to instabilities from qualitative indications: steep, concave, with high topographic index; • areas with quaternary cover not very much consolidated; • torrents bed in more steep areas. 42 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Survey Geomechanics - rio Corda Where (red circles) • slopes prone to instabilities from qualitative indications: steep, concave, with high topographic index; • areas with quaternary cover not very much consolidated; • torrents bed in more steep areas. 42 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Survey Geomechanics - rio Corda Where •Point 1 is localized on the bed of Poia torrent, close to a slit dam, •Point 2 is on the landslide of june 2008; •Point 3 and 4 are close to a landslide deposit, close to a detachment niche. 43 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Survey Geomechanics - rio Corda Where •Point 1 is localized on the bed of Poia torrent, close to a slit dam, •Point 2 is on the landslide of june 2008; •Point 3 and 4 are close to a landslide deposit, close to a detachment niche. 43 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Analysis Geomorphology - Canali Slopes 44 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Analysis Geomorphology - Canali Statistics Sintesys: mean slope: 34° max slope: 87° min slope: 0° 45 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Analysis Geomorphology - Val di Case Network delineation Networks from DEM in red and ufficial network from P.A.T. (blue) 46 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Analysis Geomorphology - Val di Casa Subnetworks From the resuts of the previous analsys follow the decision to consider some basins which are those from which the sediment delivery is assumed to mainly come. 47 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Now the Choice of models 48 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Two directions Subsurface waters - Surface waters Sediment is generated Sediment is found by landslides that in the subsequently turn into bed of torrents debris flow and areas close by 49 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Two directions Subsurface waters - Surface waters Sediment is generated Sediment is found by landslides that in the subsequently turn into bed of torrents debris flow and areas close by Subsurface water flow Rainfall-Runoff model Modeling 50 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Two directions Subsurface waters - Surface waters Sediment is found Sediment is generated in the by landslides that bed of torrents subsequently turn into and areas close by debris flow and by hillslope inputs Subsurface water flow Rainfall-Runoff model Modeling 51 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Use empirical laws Subsurface waters A prototype is 52 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 There is a geotechnical model c s z cos2 ⇥s w ⇤w cos2 ⇥sFS = + tan ⌅c tan ⌅c s z cos ⇥s sin ⇥s s z cos ⇥s sin ⇥s s z cos ⇥s sin ⇥s where: Symbol Name nickname Unit FS Factor of Safety fos [/] c⇥ cohesion chsn [M L2 T 2 ] ⌅c columbian friction angle cfa [/] ⇤w position of the water table surface pwts [L] z depth of soil ds [L] s soil/terrain density std [M L 1 T 2 ] w density of liquid water dlw [M L 1 T 2 ] ⇥s slope of terrain surface sts [/] 53 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 And a hydrological model often assuming stationary hydrology 54 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Sediment availability playing with simplified models One idea is to use to make reasonable experiments models like SHALSTAB and SINMAP (the method itself is not rigorous, but its exploration allows to frame the quantities). For instance assigning a rainfall with a certain duration and intensity (according to Intensity-duration-frequency curves), Equation for stability can be inverted ... In the hypothesis that short term rainfall do not destabilize the hillslopes: ⇥ T sin s ⇥w tan s c (1 + tan s ) 2 A/b ⇤ 1 + q ⇥s tan ⇤c tan ⇤c ⇥s g · z 55 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Sediment availability where: Symbol Name nickname Unit FS Factor of Safety fos [/] c⇥ cohesion chsn [M L2 T 2 ] ⌅c columbian friction angle cfa [/] ⇤w position of the water table surface pwts [L] z depth of soil ds [L] s soil/terrain density std [M L 1 T 2 ] w density of liquid water dlw [M L 1 T 2 ] ⇥s slope of terrain surface sts [/] 56 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Sediment availability ⇥ T sin s ⇥w tan s c (1 + tan s ) 2 A/b ⇤ 1 + q ⇥s tan ⇤c tan ⇤c ⇥s g · z From which one can derive an estimate of tan ⇤s f (ks , z, q, s , ⇥w , ⇥s ) a minimal value of the critical angle tan s 57 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Sediment availability and obtain maps like this one 58 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Sediment availability At this point using the reference value of the critical angle one can obtain those point where the contributing area is unstable. ⇥ T sin ⇥s ⇤w tan ⇥s c (1 + tan ⇥s ) 2 A/b ⇤ 1 + q ⇤s tan ⌅c (5, 24) tan ⌅c (5, 24) s · z Where c (5, 24) indicates that the value has been obtained in “back analysis” with precipitation of 24 hours of duration 24 hours and return period of 5 year. 59 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Analisi Geologica Analisi del sedimento disponibile - rio Corda Analisi di stabilità condotta con Shalstab per diversi tempi di ritorno. Sono riportati i dati relativi a precipitazioni con un tempo di ritorno di 30 anni. 60 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Improving the method Subsurface waters The method can be improved under many aspects •one can consider instead of a single value for a critical angle many values, depending on lithology; •one can consider different couples of rainfall-duration •instead of considering SHALSTAB one can use QD-SLAM (es. Borga et al., 2002) or CI-SLAM (Lanni et al., 2012) models that remove the hypothesis of stationarity 61 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Different choice of the geotechnical model where: 62 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 3 4 5 Different choice of the hydrological model 6 7 8 9 10 Figure 1. A flow chart depicting the coupled saturated/unsaturated hydrological model 11 developed in this study. Lanni et al., 2012 63 12 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Improving the method Subsurface waters Lanni et al., 2012 64 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Summary Subsurface waters Rio  Corda    sx Rio  Corda  dx soil  volume soil  volume Return  period 1m 2m 1m 2m 30  years 4.02E+05 8.03E+05 4.66E+05 9.32E+05 100  years 4.13E+05 8.27E+05 4.77E+05 9.55E+05 200  years 4.20E+05 8.41E+05 4.87E+05 9.75E+05 This is an exemplificative table. The error can be very large but gives, at least, an order of magnitude 65 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Gological Analysis Sediment available- Cismon When the geological analysis gave soil depth, These can (must) be used in the procedure. 66 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Analysis Sediment available- Val di Casa The sediment availability can be given also for any subbasin: 67 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Geological Analysis Sediment available- Val di Casa Therefore: The volumes of movable sediments for the Val di Casa basin. In this case the soil depth is taken constant. But clearly a better estimation can be done. The volumes obtained are consisten with the historical analysis. 68 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Can this sediment arrive to the river and being transported downstream ? We do not have at the moment rigorous analysis for assessing this. However some empirical formula can help. http://www.illustrationsource.com 69 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Sediment available Cismon On the left the areas which are thought to supply sediment to the network; on the right: the same areas with depicted the soil depth. 70 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Sediment available Cismon This can be considered a zeroth-order estimation of the possibility of the subsequent transport in channels estimated with the good old method by Takahashi (1978). C ( s / w 1) tan ⇥s ⇤ tan ⇤c h0 /n d + C ⇥ ( s / w 1) + 1 Symbol Name nickname Unit C Concentrazione in volume particelle sedimento cvps [/] h0 tirante idrico superficiale tis [L] n numero di strati di particelle movimentati nsp [/] d granulometria del sedimento gs [L] The result in the next page 71 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Sediment available Cismon According Takahashi (1978) the values of the ratio ho/nd that cause a debris flows are between 0 e 1.33. For values less than 0 the debris is dry, and with slope allowing a landslide is generated. According to the method the values of slopes which generate debris flow are in between: C ( s / w 1) C ( s/ w 1) tan ⇤c ⇤ tan ⇥s ⇤ tan ⇤c C ⇥ ( s / w 1) + 1 1.33 + C ⇥ ( s / w 1) + 1 For slopes less than the right limit, the transport is usually normal solid transport (hyperconcentrated); for slopes larger than the left limit the movent happens also in dry conditions, and therefore the sediment accumulate with difficulty on the slopes. 72 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Sediment available Cismon The network classified according to Takashi. In red the channels where debris flow is possible, in light blue the channels where possibly sediment transport is possible 73 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Sediment available Cismon The same as the previous side but with the sources of sediment enlightened. 74 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Surface Hydrology 75 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Now the sediment is in the channels We need the water to move it ! 76 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Rainfall-Runoff Analysis •There are many models that produce discharge at a catchment closure. As soon as they are appropriately calibrated, many of them are good. The problems arise when we do not have data to calibrate them 77 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Rainfall-Runoff Analysis One important question is: how do we estimate the rainfall volumes that transform into discharges (i.e. the effective rainfall) ? There exists many methods. Some are better. We cannot rely on methods introduced for agricultural settings. Obviously the choice of this method and its appropriateness affect the final result. 78 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Rainfall-Runoff Analysis There are some issue related to the problem under analysis, and some issue related to rainfall-runoff in general This problem: one wants discharges in several point, for instance for estimating sediment transport in the channel highlighted in blue 79 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 So, the basin needs to be appropriately subdivided and the hydrology appropriately estimated. This is trivial indeed ... if the model parameters depends on spatial knowledge, and can be Uphill basin rescaled! Interbasin 80 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Rainfall-Runoff Analysis I prefer those methods which use explicitly the knowledge of geomorphology Please keep also in mind that having liquid discharges are just one step of the process that involve also sediment and the use of hydraulic models 81 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Hydrological Analysis do it the PeakFlow way!Peakflow:•Assume saturation excess mechanism (and estimate the saturated areas with thetopografic index, e.g. Beven, 2001)•Use the rescaled width function (Rinaldo et al., 1995, D’Odorico e Rigon,2003) to obtain the surface and the subsurface hydrographs 82 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Hydrological Analysis do it the PeakFlow way!•Peakflow•Allows to estimate the maximum discharges (and the peak time and the criticalduration of rainfall) generated by uniform precipitation with assigned returnperiod (using a power law type of IDF) uDig implements it! 83 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Hydrological Analysis Rescaled distances (Rinaldo et al., 1995) Distances from the outlet (on the left) and rescaled (on the right). Only 40% of the areas is actually colored according to the Beven and Kirby’s (1979) topographic index. 84 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Hydrological Analysis Rescaled distances (Rinaldo et al., 1995) 85 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Hydrological Analysis Rescaled distances (Rinaldo et al., 1995) Histogram of areas that affects overland flow, assuming just 40% of area saturated. 86 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Hydrological Analysis do it the PeakFlow way! Knows your parameters (e.g. D’Odorico and Rigon, 2003): • The fraction of saturated area is a critical parameters with which the peak discharge grows approximately linearly •Velocity of water in channels and hillslope are some average in space (over the basin) and time (during the hydrograph) of the real (local) velocity •rescaled factor between channel flow velocity and overland flow in hillslope (and the ratio between s channel flow and subsurface velocity) 87 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Hydrological Analysis do it the PeakFlow way! 88 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 The question of solid discharges We need now to invent a model for associating the solid discharges to the liquid ones that we have obtained so far. We do not have ... but we could envision how to do it: •Built the total quantity of sediment available at distance say, x, to build the sediment width function (normalized by the total volume) •Assume that water and sediment in channel have the same velocity •Built the sediment hydrograph 89 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Solid Discharges •Assume that all the sediment movements trigger at the same instant •The sediment width function (after transforming space into time) IS the sediment hydrograph, and you add it to the water hydrograph for the final result. Do it but with care! 90 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Hydraulics 91 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Solid Discharges •Sediment concentration could be too high. In this case the sediment deposit. It is clear that from the point you add sediment and water in input one should use an effective hydraulic model to move it along channels. This is actually another Job and we do not talk about here 92 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 A minimal approach to sediment delivery on alluvial fans 93 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 A minimal approach to sediment delivery on alluvial fans Sheidl and Rickenmann (2009) Will be explained in the next talk 94 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 And in short the last steps 95 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 At this point the probability of occurrence of the event (return tensity value that has been assigned. For each cell of the doma Squeeze it in return period) that, once inserted into the haz values (intensity, three colors Intensity 8.2, give three hazard values (one for each return period). High 9 8 7 6 5 4 Medium Low 3 2 1 Figure 8.2 – Hazard class matrix. High Medium Low Probability/Frequency Low Medium High Return Period The Hazard Class Matrix (Figure 8.2) proposes two different level 6; yellow or blue for level 2) for two different statistical 96 Rigon et Al. different scenarios depending on the choices made. In theseMonday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Squeeze it in three colors Depending on the type of event the choice of the probability bins change. PROBABILITY THRESHOLDS and CORRESPONDING RETURN PERIODS Low probability Tr=200 years Medium probability Tr=100 years High probability Tr=30 years Where observed events show an intensity that is reasonably greater than that corresponding to a return period of 200 years, then it may be worthwhile considering these observed situations as a further class of extraordinary hazard (residual or potential). 8.1.4 Hazard Class Matrix 97 Rigon et Al.point the probability of occurrence of the event (return period) must be associated to the in- At thisMonday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 each corresponding to a different destructive potential for the event. Each of these classes is identi- fied by means of a specific colour or symbol on the Hazard Map. Each intensity class is defined on Squeeze it in three colors the basis of damage caused (or causable) by the event. In the table below (Table 8.2) the correlation between intensity level and damage caused (or causable) is shown. The Intensity can be categorised subjectively according to Levels of Damage Table 8.2 – Description of intensity levels in relation to damage caused Intensity Level of damage High Loss of human life and destruction and/or permanent damage of structures and infra- structure (hardly ever reversible) Medium Serious damage to structures and infrastructure (without destruction), injuries to people that are rarely fatal Low Minor damage to structures and infrastructure with temporary outages of their services, no injuries to people Table 8.3 presents the threshold values prescribed for torrential phenomena by the Provincial Resol- ution of the Province of Trento, which not only considers the physical quantities of velocity and depth of the flow, but also the thickness of depositions and depth of scouring. 98 If, in applying Table 8.3, there are various scenarios with different hazards and equal probability, then the least favourable scenario is considered. Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Squeeze it in three colors Or more objectively according to the values of the dynamical parameters involved Velocity of flow Thickness of de- Intensity of the Depth of the flow outside the water- position outside Depth of scouring torrential phe- course the watercourse nomenon h [m] d[m] u [m/s] M [m] High h>1 or u>1 or M>1 d>2 Medium 0.5 < h ≤ 1 or 0.5 <u ≤1 or 0.5 < M ≤ 1 0.5 < d < 2 Low h ≤ 0.5 or u ≤ 0.5 or M ≤ 0.5 d < 0.5 From P.A.T. DGP 2759 (22/12/2006) 8.1.3 Probability thresholds Linked to the intensity threshold, the probability threshold indicates the probability of occurrence of 99 an event. The probability of a certain event occurring is evaluated on the basis of a time series of Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Squeeze it in three colorsTable 8.5 – Colours and filles to be assigned to each hazard class on the Hazard Map. Hazard Symbol Fill Ordinary classes high H4 red medium H3 blue low H2 yellow negligible H1 white residual HR Extraordinary classes potential HP grey 100 Rigon et Al.Monday, October 1, 12
  • residual HR Extraordinary classes Danube Flood Risk Conference - Trento 26 September 2012 potential HP grey Squeeze it in three colors Figure 8.3 – Example of Hazard Map that can be drafted with the methods proposed in these Guidelines. 101 8.1.5 Final Assessments Rigon et Al. The Hazard Map resulting from the intensities and probabilities of occurrence must undergo someMonday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Poste Italiane Spa - Spedizione in Abbonamento Postale 70% NE/TN - anno IV - numero 7 - marzo 2012 - Ä 10,00 SentieriUrbani LA RIVISTA DELLA SEZIONE TRENTINO DELL’ISTITUTO NAZIONALE DI URBANISTICA Issn: 2036-3109 In questo numero Urbanistica e rischio idrogeologico Urbanistica e rischio idrogeologico sezionetrentino.inu@gmail.com 102 Rigon et Al.Monday, October 1, 12
  • Thank you for your attention Read the Guidelines and the Papers for detailsMonday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Bibliografia •Beven, K J and Kirkby, M J. 1979, A physically based variable contributing area model of basin hydrology Hydrol. Sci. Bull., 24(1),43-69 •Beven, K, Rainfall-runoff modelling: the primer, Wiley, 2001 •Borga, M., G. Dalla Fontana, F. Cazorzi, Analysis of topographic and climatic control on rainfall-triggered shallow landsliding using a quasi-dynamic wetness index, Jour. Hydrol., 268, 56-71, 2002 •D’Odorico, P. and R. Rigon, Hillslope and channels contribution to the hydrologic response, Water Resour Res, 39(5) , 1-9, 2003 •Lanni, C.; McDonnell, J. J.; Rigon, R., On the relative role of upslope and downslope topography for describing water flow path and storage dynamics: a theoretical analysis, Hydrological Processes Volume: 25 Issue: 25 Pages: 3909-3923, DEC 15 2011, DOI: 10.1002/hyp.8263 •Lanni C., J. McDonnell JJ, Hopp L., Rigon R., "Simulated effect of soil depth and bedrock topography on near- surface hydrologic response and slope sta- bility" in EARTH SURFACE PROCESSES AND LANDFORMS, v. 2012, (In press). - URL: http://onlinelibrary.wiley.com/doi/10.1002/esp.3267/abstract . - DOI: 10.1002/esp.3267 •Lanni C., Borga M., Rigon R., and Tarolli P., Modelling catchment-scale shallow landslide occurrence by means of a subsurface flow path connectivity index, Hydrol. Earth Syst. Sci. Discuss., 9, 4101-4134, www.hydrol-earth-syst-sci- discuss.net/9/4101/2012/ doi:10.5194/hessd-9-4101-2012, (in press at HESS) 104 Rigon et Al.Monday, October 1, 12
  • Danube Flood Risk Conference - Trento 26 September 2012 Bibliografia •Montgomery, DR and Dietrich, WE (1994), A physically based model for the topographic control on shallow landsliding , Water Resources Research, Vol. 30, no. 4, pp. 1153-1172. 1994. •R. Rigon - Basic Notations, Un Real Books di Idrologia, DICA, Università di Trento, 2009 •Rinaldo A., G. K. Vogel, R., Rigon and I. Rodriguez-Iturbe, Can one gauge the shape of a basin?, Water Resources Research, (31)4, 1119-1127, 1995 •Sheidl, C and Rickenmann, D., (2009) Empirical prediction of debris-flow mobility and deposition on fans, Earth Surface Processes and Landforms, Volume 35, Issue 2, pages 157–173, February 2010 105 Rigon et Al.Monday, October 1, 12
  • End of AppendixMonday, October 1, 12