Flash Floods in a changing context: Importance of the impacts induced by a changing environment

Table of contents Sub Project 5 Review of current practices & past experiences Future scenarios Future risk assessment Mitigation and adaptation Conclusions

Sub project 5 FF & DF risk management and mitigation in changing environments Review of current practices & past experiences Creation of global change scenarios ▫ Climate ▫ Land-use ▫ Forest fires Development of a methodologies to assess the impacts future changes ▫ Risk mapping ▫ Rule-based system Provide guidelines for practitioners to design mitigation and adaptation measures

Review of current practices & past experiences Compilation of FF & DF follow-up studies Description of impacts Improvements on the local risk management Compilation of lessons learnt classified by ▫ Prevention ▫ Preparedness ▫ Response ▫ Dissemination and education Prevention  Risk estimation  Land use regulations  Hydrometeorological forecasting systems  Integral analysis to plan protection infrastructures  Infrastructure inventory (maintenance)  Natural floodplains (water retention)  Historical FF and DF databases (learn from past)  Future changes (i.e. climate and land use) Prevention  Risk estimation  Land use regulations  Hydrometeorological forecasting systems  Integral analysis to plan protection infrastructures  Infrastructure inventory (maintenance)  Natural floodplains (water retention)  Historical FF and DF databases (learn from past)  Future changes (i.e. climate and land use) Preparedness  Review and update emergency plans (real effectiveness)  River bed maintenance  Evacuation maps  Training and plan evacuation simulations Preparedness  Review and update emergency plans (real effectiveness)  River bed maintenance  Evacuation maps  Training and plan evacuation simulations Response  Coordination of organizations involved  Unit to monitor the post-crisis  Follow-up studies  Improve warnings transmission  Promote hydrometeorological systems  Continuous maintenance Response  Coordination of organizations involved  Unit to monitor the post-crisis  Follow-up studies  Improve warnings transmission  Promote hydrometeorological systems  Continuous maintenance Dissemination and education  Exchange between experts  Diversify the mechanisms to disseminate  Risk culture: o sociological surveys o flood marks o hazard maps o …  Education programmes at schools Dissemination and education  Exchange between experts  Diversify the mechanisms to disseminate  Risk culture: o sociological surveys o flood marks o hazard maps o …  Education programmes at schools

Creation of global change scenarios Future climate scenarios ▫ Extreme precipitation assessment Future land-use scenarios ▫ Urban land-use ▫ Rural land-use Future forest fires scenarios

Future climate scenarios Llobregat basin Data used Models validation Temporal future trends Future spatial patterns Institution Downscaling method Model Output resolution SRES scenarios Control period Future scenarios GCMRCM SMCDynamical ECHAM5- MPIOM MM515 km, 6hA2, B ObservationsAltava-Ortiz3 km, daily MPI-METDynamicalECHAM5-r3REMO25 km, dailyA1B METO-HCDynamicalHadCM3Q0HadRM3Q025 km, dailyA1B ObservationsSpain 0220 km, daily

GEV fitted to the annual maxima daily precipitation for the observations ( ), the control ( ) (dashed) and the climate models results ( ) (solid) showing the minimum and maximum intensity in the Llobregat basin Extreme precipitation assessment Generalized Extreme Value functions Future scenarios; periods of 30 years High variability and uncertainty Future climate scenarios GEV fitted to the annual maxima daily precipitation for the control ( ) and future periods simulated with SMC for the A2 scenario in the south Llobregat basin

Future land-use scenarios Urban land-use Corine database JRC’s MOLAND model Urban land-use maps in the south Llobregat basin coming from Corine database (2000) and MOLAND A2 future scenario (2040)

Future land-use scenarios Rural land-use Eururalis project data Llobregat 2000Llobregat 2030 A1 Llobregat 2030 A2Llobregat 2030 B1Llobregat 2030 B2

Forest fires scenarios Canadian Drought Code Depends on T and P Validation with actual forest fires Daily calculation of CDC > 400 Annual CDC computed on the Llobregat basin during the historical period. The highest value occurred in 1994 when the most significant forest fire occurred. Historical and future scenarios of CDC on the Llobregat basin based on observations and SMC climate scenario A2 for three time periods

Future risk assessment Risk = Hazard x Exposure x Vulnerability Low Llobregat basin, showing the flood plains for a 500 year return period event. Llobregat basin I – T relationship for a 24 h duration for the A2 SRES scenario, for the control period and the future scenario Weighing function to update the hazard values for the future rainfall scenarios.

Future risk assessment Risk = Hazard x Exposure x Vulnerability Urban land use in the Low Llobregat area: Urban land use from Corine 2000 (a); and A2 urban land use scenario for 2040 (b). Vulnerability map for the A2 land use scenario for 2040.

Future risk assessment Overlaying the three variables and multiplying the weights Vulnerability Hazard Risk maps for the south Llobregat basin for the (a) current situation (2000), (b) future A2 – A2 scenario (2040) (c) and its difference

Rule based system Forecasting system that allows to link real-time observed values with expected hazard in probabilistic terms ▫ Simplification of a hydrological model with shorter lead times ▫ Operational use: issue warnings ▫ Considering high percentiles to represent extreme events Governing variables for FF ▫ Antecedent soil moisture ▫ Forecasted rainfall

Rule based system Anoia basin ▫ Ocurrence  Moderate increase  Two exceptions ▫ Intensity  Generalized increase  Even for the exceptions Period# POT per year (for each sub-period) Control ( ) Scenario A2 ( ) Scenario B1 ( ) GP distribution fitted to the POT discharge values of the Anoia sub-basin for the control ( ) and future periods for the A2 (left) and B1 (right) scenarios. Time series of the discharge values in the Anoia sub-basin.

Mitigation and adaptation Important changes may occur, but uncertainties are high and difficult to assess Change of paradigm must be done: ▫ From «Fighting against Floods» to «Living with floods»

Mitigation and adaptation Implementation of EC Floods Directive and development of FRMP is crucial ▫ Promoting communication and creating a risk culture ▫ Implementing non-structural measures, which are robust and win-win  Early warning systems  SUDS  Local mitigation strategies (involving the population)  Etc.

Conclusions Climate projections strongly depend on models ▫ Need for further research ▫ Regionalized models are crucial High variability and uncertainties ▫ Present everywhere ▫ Specially for extremes ▫ Use results with care Mitigation and adaptation ▫ Implementation of EC Floods Directive is crucial ▫ Change of paradigm is needed ▫ Non-structural measures must be used

Marc Velasco Àngels Cabello