Geomorphic Approaches for the Delineation of Flood Prone Areas

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Junior Enrico Marchi Lecture at the University Roma Tre, 23 May 2014.

Junior Enrico Marchi Lecture at the University Roma Tre, 23 May 2014.

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  • 1. 1/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Salvatore Manfreda Università degli Studi della Basilicata salvatore.manfreda@unibas.it Geomorphic Approaches for the Delineation of Flood Prone Areas
  • 2. 2/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Collaboration The present activity have involved a significant number of colleagues that I would like to acknowledge n  Domenico Capolongo, n  Francesco De Paola, n  Margherita Di Leo, n  Vito Iacobellis, n  Mauro Fiorentino, n  Andrea Gioia, n  Maurizio Giugni, n  Salvatore Grimaldi, n  Fernando Nardi, n  Alberto Refice, n  Giorgio Roth, n  Caterina Samela, n  Aurelia Sole, n  Angela Celeste Taramasso, n  Tara Troy.
  • 3. 3/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Flood Exposure at the Global Scale Flooding is evident in more than 1/3 of the world’s land area, in which some 82% of the world’s population resides. Dilley  et  al.  (2005)  
  • 4. 4/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Flood Monitoring Rela5vely  poor  density  of  gauging  sta5ons  in  some   regions,  such  as  South  America,  Asia  and  Africa.   Herold  and  Mouton  (HESSD,  2011)  
  • 5. 5/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Are Natural Hazard increasing? There is a significant increase of the economic losses for weather related events Flooding 21% CuJer  and  Emrich  (EOS-­‐  2005)  
  • 6. 6/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Number of Reported Events Much of the increase in number may be due to improvements in information access, but the rising of flood and cyclones events is dramatic compared to others. Peduzzi  (2005)  
  • 7. 7/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Flood Mapping ü There is a significant effort in flood mapping at different scales collecting all available information (e.g. Dilley et al., 2005; Moel et al., 2009) or using large scale physically based models of rainfall-runoff and river routing (e.g. Pappenberger et al., 2012; Winsemius et al., 2013). ü The full mosaic is not available yet, but it may be extremely useful in reinsurance, large scale flood preparedness and emergency response (e.g. Kappes et al., 2012).
  • 8. 8/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Flood Mapping: Limitations Current  methods  or  products  have   some  limita5ons     •  Extent  of  the  study  area     •  Reference  basin  scale   •  Spa5al  resolu5on  adopted   •  Time  consuming   computa5on   •  Calibra5on  problems     Pappenberger  et  al.:  Deriving  global   flood  hazard  maps  (HESS  -­‐  2012)  
  • 9. 9/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 River  basin  morphology   intrinsically  contains  an   extraordinary  amount  of   informa5on  on  flood-­‐driven   erosion  and  deposi5onal   phenomena,  cons5tu5ng  a   useful  indicator  of  the  flood   exposure  of  a  given  area       (e.g.  Arnaud-­‐FasseJa  et  al.,   2009;  Tucker  et  al.,  2001;     Tucker  and  Whipple,  2002)     Geomorphic Approaches Flood  Plain  
  • 10. 10/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Geomorphic Approaches ü Following this theoretical principle, several authors have shown that the delineation of flood prone areas at the large scale can be carried out using simplified methods that rely on basin geomorphologic feature characterization (e.g., McGlynn and Seibert, 2003; Gallant and Dowling, 2003; Dodov and Foufoula-Georgiou, 2006). ü The advent of new technologies to measure topographic surface elevation (e.g., GPS, SAR, SAR interferometry, and laser altimetry) has given a strong impulse to the development of geomorphic approaches for valley bottoms identification using Digital Elevation Models (DEMs).
  • 11. 11/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Digital Elevation Models ü The increasing availability of digital terrain models has given a strong impulse to the development of so called distributed and DEM-based models. ü Digital terrain model obtained through interferometric data gathered by the space shuttle campaign by NASA with a cell- size of 90m. (CGIAR-CSI: http://srtm.csi.cgiar.org/) ü ASTER GDEM 30m available from June 2009 ( http://asterweb.jpl.nasa.gov/gdem.asp )
  • 12. 12/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Research Questions i) What are the geomorphological signatures useful for the delineation of flood prone areas? ii) Is it possible to define a simplified approach for the delineation of flood prone areas starting from DEMs? iii) is it possible to use such procedure to map the flood exposure over large scale? iv) What is the impact of scale/resolution on Geomorphic Approaches?
  • 13. 13/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Geomorphic Methods ü Three different geomorphic approaches to the identification of flood prone areas are investigated. ü The selected algorithms are: n  GM1 - modified Topographic Index (TIm) (Manfreda et al., 2011); n  GM2 - linear binary classifier applied on different geomorphic features related to the location of the site under exam with respect to the nearest hazard source (Degiorgis et al., 2012); n  GM3 - hydro-geomorphic method by Nardi et al. (2006) simulating inundation flow depths along the river valley with the associated extent of surrounding inundated areas.
  • 14. 14/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 GM1 Modified Topographic Index Stream line Contour line The concept of contributing area per unit contour length This   index   is   commonly   used   to   quan5fy   topographic   control   on   numerous   hydrological   processes,   but   it   is   also   a   good   indicator   of   flood-­‐prone   areas,   as   recently   highlighted   by   Manfreda   et   al.   (2011)  and  Jalayer  et  al.  (2014). ( ))tan(/ln βn a (Beven and Kirkby, 1979)
  • 15. 15/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 GM2: The linear binary classifiers GM2 identifies areas subject to the flooding hazard through pattern classification techniques using five morphologic features: ü 1. the contributing area, A [m2]; ü 2. the surface curvature, ∇2H [-]; ü 3. the local slope, S [-]; ü 4. the distance of each cell from the nearest stream, D [m]; ü 5. the relative elevation to the nearest stream, H [m].
  • 16. 16/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 GM3 - Hydro-geomorphic method The inundation model is defined as a function of the hydrologic characteristics of a predefined design flood event designed based on the flow peak discharge at the basin outlet. ü GM3 is an automated GIS-based procedure, implementing a set of terrain analysis algorithms for flooded area delineation by linking a simplified inundation model with the geomorphic properties of the stream network (Nardi et al., 2006; Nardi et al., 2013).
  • 17. 17/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Schematic description of the different algorithms analysed
  • 18. 18/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Some Terms FALSE   POSITIVE   FALSE   NEGATIVE  
  • 19. 19/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Accuracy, sensitivity, specificity sensitivity (rtp) = true positive fraction = 1 – false negative fraction = TP / (TP + FN) specificity (rtn) = true negative fraction = 1 – false positive fraction = TN / (TN + FP) accuracy = (TP + TN) / (TP + TN + FP + FN)
  • 20. 20/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Case Study: The Upper Tiber River Alluvial  Plain     DEM   Flood  Map   Upper Tiber Basin 5000 km2 Chiascio River 727 Km2
  • 21. 21/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Flood Map used for Calibration ü The “Piano di Assetto Idrogeologico” or PAI developed by Tiber River Basin Authority (TRBA) contains flood hazard maps based on detailed standard hydrologic and hydraulic models (TRBA PAI, 2010). ü The TRBA PAI was developed using high precision bathymetric surveys of the channel surveyed as cross sections with average spacing interval of 200-400 meters. This detailed fluvial morphology was used as main input of a 1D hydraulic models (HEC-RAS and FRESCURE). simulating the effect of the design hydrographs considering return periods of 50, 200, and 500 years.
  • 22. 22/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Results: GM1 n=0.020;  τ=3.1    
  • 23. 23/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Results: GM2 Single Features
  • 24. 24/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Results: GM2 ü ROC curves Upper Tiber Basin 5000 km2 Chiascio River 727 Km2
  • 25. 25/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Results: GM3
  • 26. 26/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Flood Maps according to the three considered methodologies
  • 27. 27/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Visual comparison of the performances of the GM1, GM2 and GM3 Zone  2   Zone  1   Zone  2  Zone  1  
  • 28. 28/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Model Intercomparison     Mod.   Topographic   Index   Single-­‐feature   binary  classifier   (H)   Hydrogeomorp hic  Method   Ideal   value   True  posiHve  rate,     90.2%   90.1%   60.1%   100%   False  negaHve  rate,     9.8%   9.9%   39.9%   0%   True  negaHve  rate,     51.4%   81.2%   97.2%   100%   False  posiHve  rate,     48.6%   18.8%   2.8%   0%    rfp  +  rfn     58.4%   28.7%   42.7%   0%       Mod.   Topographic   Index   Single-­‐feature   binary  classifier   (H)   Hydrogeomorp hic  Method   Ideal   value   True  posiHve  rate,     93.8%   93.4%   75.8%   100%   False  negaHve  rate,     6.2%   6.6%   24.2%   0%   True  negaHve  rate,     61.3%   66.4%   94.3%   100%   False  posiHve  rate,     38.7%   33.6%   5.7%   0%   rfp  +  rfn     44.9%   40.2%   29.9%   0%   Upper Tiber Basin 5000 km2 Chiascio River 727 Km2
  • 29. 29/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 DEM Resolution affects on morphological indexes (Wood, 1996)
  • 30. 30/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Scale Dependence of the Modified Topographic Index The spatial distribution of the topographic index is inevitably linked to the cell-size of the adopted DEM (Zhang and Montgomery, 1994). This d e p e n d e n c e i s i n v e s t i g a t e d comparing the errors rfp and rfn obtained using the modified topographic index computed from DEMs with different cell-size. Analyses were carried starting from DEM with cell-size of 20m up to 720m.
  • 31. 31/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Scale Dependence and Associated Errors 11 10 2 3 4 5 6 7 8 9 1 ARNO Sub-catchments Less  sensi5ve  to  the   change  of  resolu5on  
  • 32. 32/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Future directions New strategies for flood modelling calibration ü Notwithstanding the limitation of the flood map adopted for comparison, it would be extremely useful to have flood map of real event. ü In this respect, a possible contribution may arise from the remote sensing that is developing a number of applications for flood mapping using Synthetic Aperture Radar (SAR).
  • 33. 33/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Future Direction: Synthetic Aperture Radar Remote Sensing J.A. Richards, Remote Sensing with Imaging Radar, Springer, 2009 Basic principle: water-covered surfaces appear darker than non- water ComplicaHng  factors:   o  speckle   o  water:   §  wind;  waves;  vegeta5on…   o  non-­‐water:   §  crops;  forest;  urban,…   SAR intensity thresholding
  • 34. 34/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 An Example (h(At)-H)/D Inundated  area   Inundated area Orthophoto  
  • 35. 35/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Conclusion ü Geomorphic approaches represent a useful tool for preliminary studies on flood prone areas or to extend flood mapping over large areas. ü These methods can be improved or integrated using available knowledge on limitations and prerogatives of different algorithms. ü This approaches may benefit from advances in remote sensing techniques and vice versa. ü Sensitivity of Geomorphic approaches is not influenced by cell-size resolution changes (from 20m-100m) or basin size. This open the perspective of using these methods for downscaling procedures in global flood mapping.
  • 36. 36/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014
  • 37. 37/37 2014 Junior Enrico Marchi Lecture Dipartimento di Ingegneria – ROMA TRE Roma – 23 May 2014 Related Publication Samela, C., S. Manfreda, F. De Paola, M. Giugni and M. Fiorentino, Dem-based approaches for the delineation of flood prone areas in an ungauged basin in Africa, Journal of Hydrologic Engineering, 2014. Manfreda, S., F. Nardi, C. Samela, S. Grimaldi, A.C. Taramasso, G. Roth, A. Sole, Investigation on the Use of Geomorphic Approaches for the Delineation of Flood Prone Areas, Journal of Hydrology, 2014. Manfreda, S., C. Samela, A. Sole and M. Fiorentino, Prone Areas Assessment Using Linear Binary Classifiers based on Morphological Indices, ASCE-ICVRAM-ISUMA 2014, 2014. Manfreda, S. and Sole, A. ”Closure to “Detection of Flood-Prone Areas Using Digital Elevation Models” by Salvatore Manfreda, Margherita Di Leo, and Aurelia Sole.” Journal of Hydrologic Engineering, 18(3), 362–365, 2013. Manfreda, S., M. Di Leo, A. Sole, Detection of Flood Prone Areas using Digital Elevation Models, Journal of Hydrologic Engineering, Vol. 16, No. 10, September/October 2011, pp. 781-790 (10.1061/ (ASCE)HE.1943-5584.0000367), 2011. Fiorentino, M., S. Manfreda, V. Iacobellis, Peak Runoff Contributing Area as Hydrological Signature of the Probability Distribution of Floods, Advances in Water Resources, 30(10), 2123-2144, 2007. Manfreda, S., A. Sole, e M. Fiorentino, Valutazione del pericolo di allagamento sul territorio nazionale mediante un approccio di tipo geomorfologico, L'Acqua, n. 4, 43-54, 2007 (In Italian). Manfreda, S., A. Sole, M. Fiorentino, Can the basin morphology alone provide an insight on floodplain delineation?, on Flood Recovery Innovation and Response, WITpress, 47-56, 2008.