1.0 - Flood hazard: overview

RISK

=

HAZARD

×

EXPOSURE

×

COPING FACTOR

Event probability, Return Period

Goods, people and services exposed

Emergency plans, adaptation strategies

1.1 - Flood hazard: overview

Methods used to obtain hazard maps:

• Historical discharge and flooding records
• Documentary evidence from past events
• Local surveys
• Hydrological + hydraulical modelling

1.2 - Flood hazard: overview

Flood hazard over Italy (PRESENT DAY)

Return Period:

20-50 yrs

Return Period:

100-200 yrs

1.3 - Flood hazard: overview

Flood hazard over Italy (FUTURE CHANGE)

• Several studies available
• No study specific to Italy
• Relatively low resolution (>5km)
• No flood extents, only flood proxies (extreme discharge)

Results over Italy:

• General increase in flood proxies by the end of the century
• Especially for Northern Italy
• Low resolution does not resolve smaller basins

2.0 - The GRIPHO dataset

Two main goals:

• Driving the hydrological model with high resolution data
• Validating the regional climate simulations

Data provided by Marco Verdecchia (CETEMPS):

• 2001 - present
• Hourly
• 3712 stations
• No quality check

2.1 - The GRIPHO dataset

Issues:

• Varying station availability and density across the domain
• Inconsistencies, outliers and data errors
• Only ~15 years or data

Strong points:

• High station density (~1 station/100km²)
• High temporal resolution (1 hour)
• Only high resolution station-based dataset covering all Italy

2.2 - The GRIPHO dataset

Cleaning procedure

2.3 - The GRIPHO dataset

Gridding

• 12km Lambert Conformal Conic grid

• Gridding method based on Delaunay polygons using SciPy's interpolate.griddata

• Simple, fast method which minimizes smoothing
• Similar to Norway's KLIMAGRID dataset (Mohr, 2008, 2009)
• NetCDF CF-compliant output format

Mohr M., 2008: New Routines for Gridding of Temperature and Precipitation Observations for seNorge.no

Mohr M., 2009: Comparison of versions 1.1 and 1.0 of gridded temperature and precipitation data for Norway

Velasquez N. et al., 2011: Rainfall distribution based on a Delaunay triangulation method

2.4 - The GRIPHO dataset

Validation (mean PR, detail)

2.5 - The GRIPHO dataset

Validation (R95ptot, detail)

2.6 - The GRIPHO dataset

Conclusions

• Performance in the North similar to other high resolution datasets (EURO4M-APGD, ARCIS)
• Much finer details compared to HMR and E-OBS, especially for extremes
• Only station-based dataset over Italy providing hourly precipitation

Outliers

2.x - The GRIPHO dataset

2.x - The GRIPHO dataset

Validation

2.x - The GRIPHO dataset

Validation

2.x - The GRIPHO dataset

Validation (PDF, detail)

2.x - The GRIPHO dataset

2.x - The GRIPHO dataset

Automated filtering

• Removal of extreme values > 200 mm/h
• Removal of isolated > 100 mm/h reports
• Removal of complete months with > 1800 mm (2.5 mm/h)
• Removal of continuous identical values

Rauthe et al. 2013; A Central European precipitation climatology–Part I: Generation and validation of a high-resolution gridded daily data set (HYRAS)

Isotta et al. 2013; The climate of daily precipitation in the Alps: development and analysis of a high‐resolution grid dataset from pan‐Alpine rain‐gauge data

Perry et al., 2009; The generation of daily gridded datasets of temperature and rainfall for the UK

Hiebl et al., 2017; Daily precipitation grids for Austria since 1961—development and evaluation of a spatial dataset for hydroclimatic monitoring and modelling

2.x - The GRIPHO dataset

Flagging

• Total % of valid values
• Total % of valid values ≠ 0
• % of events > mean + {10,15,25} SD
• % of events > median + {10,15,25} IQR
• % of events with 50 < pr < 100mm/h
• % of events with pr > 100mm/h
• % of the top {1,5,10} most common values

Manual filtering on a monthly basis

2.x - The GRIPHO dataset

2.x - The GRIPHO dataset

Results on warning flags

3.0 - Regional Climate Model

Two RegCM 4.6.1 12km EURO-CORDEX simulations run on ICTP's Argo and CINECA's Marconi clusters:

1. ERA-Interim driven 1979-2016 historical simulation
2. HadGEM driven 1971-2099 scenario simulation (RCP8.5)

• 135 3-year tuning experiments
• 6000 runtime hours
• 3 million core-hours
• >100TB disk usage

Thanks to James Ciarlo` for running part of the HadGEM driven simulation!

3.1 - Regional Climate Model

MEAN PR VALIDATION

3.2 - Regional Climate Model

3.3 - Regional Climate Model

3.4 - Regional Climate Model

3.5 - Regional Climate Model

Conclusions

• Model precipitation and temperature generally in line with observations
• Increased projected average precipitation by the end of the century in winter in the north; decrease in the south and isles in summer
• Precipitation extremes projected to strongly increase

3.x - Regional Climate Model

3.x - Regional Climate Model

3.x - Regional Climate Model

3.x - Regional Climate Model

3.x - Regional Climate Model

3.x - Regional Climate Model

TAS

PR

3.x - Regional Climate Model

3.x - Regional Climate Model

3.x - Regional Climate Model

3.x - Regional Climate Model

4.0 - Cetemps Hydrological Model

CHyM Is a distributed (gridded) hydrological model. Peculiarities:

• Can build DEM from various sources, smoothing by cellula automata algorithms
• Can use several kind of inputs, such as station observations, gridded model data, etc.
• Designed to work on any domain
• Used daily at CETEMPS for operational forecasts
• Hourly NetCDF output

4.1 - Cetemps Hydrological Model

• 9 simulated domains
• Tested several Digital Elevation Models, chose HydroSHEDS
• Specific tuning for each region
• 300-900m resolution
• Argo and Marconi clusters
• 3000 runtime hours
• 100k core-hours
• ~35TB

Three drivers:

• GRIPHO (MM5) 2001-2016
• RegCM-ERA       1980-2016
• RegCM-HAD      1972-2099

4.2 - Cetemps Hydrological Model

4.3 - Cetemps Hydrological Model

MEAN DISCHARGE

4.4 - Cetemps Hydrological Model

MEAN ANNUAL MAXIMUM DISCHARGE

4.5 - Cetemps Hydrological Model

100-YEAR ESTIMATED DISCHARGE

GRIPHO

HadGEM

present

HadGEM

2020-2049

HadGEM

2070-2099

100-year discharges estimated following:

Maione et al., 2003: Regional estimation of synthetic design hydrographs

Thanks to Francesca Raffaele for the research work!

4.6 - Cetemps Hydrological Model

Conclusions

• Model discharges in line with observations, for the few available stations
• Average discharge projected to slightly increase in the north; mixed changes in the rest of the domain/seasons
• Extreme discharges projected to strongly increase by the end of the century (often >1.5x)
• Signal very dependent on the region and season

4.x - Cetemps Hydrological Model

96 river network reconstruction tests for each region

(manual and automatic, with distance measures)

4.x - Cetemps Hydrological Model

CHyM-OP reproduced domains:

4.x - Cetemps Hydrological Model

CHyM-OP reproduced domains:

4.x - Cetemps Hydrological Model

4.x - Cetemps Hydrological Model

So far:

• Performed ~2000 model simulations to find the best configuration for the river network reconstruction
• Identify and compare the reconstruction of the Po river with different metrics: mean distance, basin area, distance Q95...

4.x - Cetemps Hydrological Model

5.0 - CA2D hydraulic model

2D flood inundation model from Dottori and Todini, 2010, 2011, modified by Rita Nogherotto to run in parallel

5.1 - CA2D hydraulic model

• 90m resolution
• HydroSHEDS DEM and river channels
• "Virtual stations" cover all domains every 5km
• Normalization with 1.5-year return period flood level
• Still ongoing, currently completed only for CHyM (GRIPHO)

5.2 - CA2D hydraulic model

5.3 - CA2D hydraulic model

Conclusions

• Encouraging initial results
• Good results in the case study
• General agreement with ISPRA maps

5.x - CA2D hydraulic model

5.x - CA2D hydraulic model

"Virtual stations"

6.0 - Summary

New data:

• New state of the art GRIPHO precipitation dataset
• Two new RCM EURO-CORDEX simulations
• Three new high resolution CHyM hydrological simulations

6.x - Visualization

An R/Leaflet tool for flood, river, DEM, basin and station visualization

6.x - Visualization

Click_edit: an R/Shiny tool for WYSISYG editing of NetCDF files