First steps in flood risk assessment over Italy in a climate change scenario

Adriano Fantini

3rd year PhD Course in Earth Science, Fluid Dynamics, and Mathematics

Supervisor: Erika Coppola

 

ADRIANO.FANTINI@phd.units.it

Aims

  • Flood risk mapping over Italy
  • scientific, reliable approach
  • future projections

Models

  • ICTP RegCM and other Regional Climate Models
  • CHyM hydrological model
  • CA2D hydraulic model

Project overview

Participants

  • Erika Coppola
  • Rita Nogherotto
  • Filippo Giorgi
  • Adriano Fantini
  • Francesca Raffaele

Methodology

Precipitation:

  • Observations
  • RCM output

Gridded netCDF:

  • River network
  • Discharges

hydrological model

For each RP, cell:

  • Gumbel distr
  • Hydrographs

Statistical RP analysis

CA2D model

For each RP, cell:

  • Flood extent
  • Flood depth

(multiple simulations)

  • RCM output
  • Discharges
  • Past floods

Validation for

1.0 - Observations

We have access to several Italian observational datasets provided by the University of L'Aquila for:

  • temperature
  • precipitation
  • water level
  • discharge

1.1 - Observations

Some examples...

Outliers

1.2 - Observations

FIRST-STAGE FILTERING

FLAGGING

FLAG CHECKING

CLEANED DATASET!

1.3 - Observations

Presented at HyMeX workshop; Barcelona, 2017

Possible first-stage filtering procedures

  • 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

 

1.4 - Observations

Possible flagging procedures

  • Mean + n*SD threshold
  • Median + n*IQR threshold
  • Peaks in the values distribution
  • Isolated dry/wet event flagging
  • Low correlation of close stations
  • ...?

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

 

1.5 - Observations

  • Visual comparison of maps/videos
  • Visual comparison of close timeseries
  • Comparison with daily datasets (EURO4M-APGD, E-OBS, ...)
  • Comparison with hourly datasets (PERSIANN, ...)
  • ...?

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

 

Possible flag-checking procedures

1.6 - Observations

Results so far...

(by applying first-stage filtering procedures only)

Before After Diff
Total valid values 250M 243M -2.6%
Total flags 324468 58008 -82.1%
pr > Mean + 20SD  3240 2538 -21.7%
pr > Median + 20IQR  49753 22519 -54.7%
pr > 100 mm/h  221822 711 -99.6%
Other softer flags 49646 32240 -35.1%

1.7 - Observations

FILTERED

ORIGINAL

1.8 - Observations

Monthly averages

1.10 - Observations

REMOVED!

1.9 - Observations

2.0 - Regional Climate Models

RCMs will be used later in the project to provide gridded input data to the CHyM hydrological model for future projections under climate change scenarios.

  • Continue ongoing EURO-CORDEX simulations on Argo and on Marconi
  • Test and validate post-processing scripts provided by eXact-lab (still ongoing)

2.1 - Regional Climate Models

We have assessed the performance of 9 RCMs over 9 regions for precipitation:

  • High resolution observations
  • Several metrics, with focus on extreme precipitation
  • We found consistent added value in higher-resolution modelling (12km vs 50km) for most regions and most models

2.2 - Regional Climate Models

I performed more than 100 model simulations over the EURO-CORDEX domain in both Argo and CINECA's Marconi A1/A2

  • Model tuning
  • Performance assessment
  • PRACE proposal 2016153590 approved

3.0 - 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
  • NetCDF output

3.1 - Cetemps Hydrological Model

Successes so far:

  • Model now working on all test domains
  • Model code and design has been streamlined (thanks to Fabio di Sante!)
  • We can reproduce past results (Coppola et al. 2013) on our test domain (western Po basin)
  • HR DEMs working (at low model res)

3.2 - Cetemps Hydrological Model

CHyM-OP reproduced domains:

3.3 - Cetemps Hydrological Model

CHyM-OP reproduced domains:

3.4 - Cetemps Hydrological Model

3.5 - 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...

3.6 - Cetemps Hydrological Model

3.7 - Cetemps Hydrological Model

4 - Statistics

How to estimate hundred-years floods with only a few (~20) years worth of data?

The methodology is taken from Maione et al., 2003

Annual maxima

Gumbel extreme value distribution

Fit parameters

SDH: "Typical" flood timing curve for each river cell

CA2D input data

5.0 - CA2D hydraulic model

After using LISFLOOD-FP, we switched to the food inundation model from Dottori and Todini, 2011

  • DEM
  • D4 River network
  • SDH

5.1 - CA2D hydraulic model

Problems!

  • Excessive flooding in low RPs
  • Not enough difference between RPs

Solutions?

  • Higher resolution (~50m)
  • Better DEMs (HydroSHEDS)
  • ?

6.0 - Visualization

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

6.3 - Visualization

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

Thanks for your attention!

Precipitation:

  • Observations
  • RCM output

Gridded netCDF:

  • River network
  • Discharges

hydrological model

For each RP, cell:

  • Gumbel distr
  • Hydrographs

Statistical RP analysis

For each RP, cell:

  • Flood extent
  • Flood depth

(multiple simulations)

  • RCM output
  • Discharges
  • Past floods

Validation for

  • EGU General Assembly, Vienna 2017, attended;
  • ICTP CHyM Workshop, Trieste 2017, oral presentation;
  • 10th HyMeX workshop, Barcelona 2017, oral presentation;
  • AGU fall meeting, New Orleans 2017, poster

CA2D model

adriano.fantini@phd.units.it

Precipitation:

  • Observations
  • RCM output

Gridded netCDF:

  • River network
  • Discharges

hydrological model

For each RP, cell:

  • Gumbel distr.
  • Hydrographs
  • Extreme Q

Statistical analysis

For each RP, cell:

  • Flood extent
  • Flood depth

(multiple simulations)

  • RCM output
  • Discharges
  • Past floods

Validation and change for

CA2D hydraulic model

Based on Maione et al., 2003

(over nine domains)

ESFM 2016-2017 report (II year)

By odineidolon

ESFM 2016-2017 report (II year)

Presentation for II year of PhD, 15 min

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