.png){kind=logo}
RAINFALL AND FLOODS
MODEL
You will find on this page all the information relating to the constitution of the model for the "Rainfall and floods" hazard for the analyzes carried out on Bat-ADAPT: ​
-
The Europe climate exposure analysis model for the "Rainfall and floods" hazard
-
The raw climate exposure indicators
-
The maximum daily precipitation (RX1DAY)
-
-
-
The France climate exposure analysis model for the "Rainfall and floods" hazard
-
The raw climate exposure indicators
-
The deviation of extreme daily precipitation (ECARTPQ99)
-
-
The raw territorial exposure indicators
-
The municipal zoning of risk prevention plans (PPRi)
-
The number of CatNat ordersby municipality (CatNat_i)​
-
Hazard levels in PPRi (PPRi_hazard)
-
-
-
The model of vulnerability to the "Rainfall and floods" hazard
RAINFALL AND FLOODS HAZARD
The model for analyzing climate exposure to the “Rainfall and floods” hazard in Europe is based on 1 climate indicator:
-
Deviation from maximum daily precipitation (RX1DAY)
This information makes it possible to assess the climatic exposure of an area, compared to the climatic exposure in the rest of Europe.
Deviation from maximum daily precipitation
Definition of the indicator: This indicator represents the deviation (in percentage) of the maximum, over the year, of daily precipitation, compared to the reference period (1850-1900). The maximum daily precipitation indicates the day in the year when it rains the most (over the whole day).
Indicator ID: EU_RX1DAY
Mesh: ~150km
Source :IPCC Interactive Atlas
Data processing: The climate data was downloaded in NetCDF format from the IPCC's interactive atlas, for the 3 scenarios (SSP1-2.6, SSP2-4.5, SSP5-8.5) and the 3 time horizons retained (short, medium and term), i.e. 9 data sets. Then, cartographic processing via the QGIS software allowed the transition from point data to data covering the whole of Europe. A legend was applied in view of the minimums and maximums existing on all the datasets.
Scope: Europe
​
In order to obtain a single exposure index revealing the climatic risk situation of a building in an area, the previous indicator was processed according to the following formulas, following to 2 cases:
​
This formula makes it possible to put the risk in a specific location into perspective in relation to the risk existing in the whole of Europe.
These are therefore compared risk ratios, to obtain an indicator varying from 0 to 100% with 0% being the minimum risk encountered in Europe from 2020 to 2100 for the 3 scenarios, and 100% the maximum risk, over this same period, for the 3 scenarios.
The exposure reliability index is assigned as follows:
5/5 Models used in the IPCC report empirically verified
4/5 Models used in the IPCC report
3/5 Other models - Very reliable
2/5 Other models - Moderately reliable
1/5 Other models - Unreliable
​
MODEL ANALYSIS OFTHE EXHIBITIONCLIMATE
IN FRANCE
RAINFALL AND FLOODS HAZARD
The model for analyzing climate exposure to the “Rainfall and floods” hazard in France is based on 1 climate indicator and 6 territorial indicators:
-
The extreme daily precipitation deviation (ECARTPQ99)
-
Communal zoning of risk prevention plans (PPRi)
-
​The number of CatNat decrees by municipality (CatNat_i)​
-
​ Areas prone to rising groundwater​
-
​ Areas subject to overflow flooding
-
Areas prone to runoff flooding
-
Hazard levels in risk prevention plans
-
The rate of soil sealing
The combination of this information makes it possible to assess the climatic exposure of an area, compared to the climatic exposure in the rest of France.
Deviation of extreme daily precipitation
Definition of the indicator: The deviation of extreme daily precipitation is given in mm, and is equivalent to the 99th percentile of intense precipitation. Precipitation is considered extreme when the cumulative precipitation for the day exceeds the reference value at the given location.
Indicator identifier: FR_ECARTPQ99
Mesh: ~8km (Safran grid)
Source :DRIAS - Meteo France
Data processing: The climate data was uploaded in CSV format to the DRIAS command space, for the 3 scenarios (RCP2.6, RCP4.5, RCP8.5) and the 5 time horizons retained (2020, 2030, 2050, 2070 and 2090), i.e. 15 data sets. Statistical processing was done to smooth the climatic variability. This involves realizing, for each time horizon chosen, the median over 20 years (10 years before and 10 after) of the climate indicator. Cartographic processing via the QGIS software allowed the transition from point data to data covering the whole of France. A legend was applied in view of the minimums and maximums existing on all the datasets.
Scope: Metropolitan France
​
Communal zoning of risk prevention plans
Definition of the indicator: This indicator indicates whether the municipality is covered by a Risk Prevention Plan for a flood-type hazard, all types combined.
Indicator ID: FR_PPRi
Mesh: Municipality scale
Source :Georisks - BD Gaspar
Data processing: The Gaspar database lists all the Natural Risk Prevention Plans which are prescribed, under review or adopted throughout France, at the municipal level. A selection of the municipalities on the metropolitan territory was made, and a second selection was made to keep only the municipalities concerned by a Risk Prevention Plan for a type of flood. Municipalities not covered are therefore not displayed in this indicator.
Scope: Metropolitan France
​
Number of CatNat decrees for floods by municipality
Definition of the indicator: This indicator indicates the number of CatNat decrees (declaration of natural disaster) having been published in each municipality of metropolitan France, for a flood-type hazard, all types combined. The Gaspar database lists all the declaration of natural disaster for compensation purposes in the face of natural disasters. In fact, the state of natural disaster recorded by decree may give rise to the right to cover for the insured against the effects of these disasters on the property covered by the insurance contracts. The count of these decrees therefore makes it possible to report on the historical loss experience of the municipality vis-à-vis floods.
Indicator ID: FR_CatNat_i
Mesh: communal
Source: Georisques - BD Gaspar
Data processing: The Gaspar database lists all of the CatNat decrees on French territory, at the level of the municipality. A selection of the municipalities on the metropolitan territory was made, and a second selection was made to keep only the municipalities concerned by declaration of natural disasters for a flood type. Finally, a count of the occurrence of each municipality was made.
Scope: Metropolitan France
​
Areas prone to groundwater rising​
Definition of the indicator: A flood is a rising groundwater type when the flood is caused by the rise in the level of the groundwater to the surface of the ground. The indicator presents the zones, in France, which are subject to this type of risk, and their level of risk (zero, flooding of basement, overflowing of groundwater).
Indicator identifier: Fr_nappes
Mesh: ~250 m (depending on the level of risk)
Source: Georisquess
Data processing: The data can be downloaded directly in cartographic format from Georisques. A processing of verification of geometries and definition of symbology according to the level of risk has been done.
Scope: Metropolitan France
​
Areas prone to overflow flooding
Definition of the indicator: The territory at high risk of flooding (TRI) by overflow is an area where the stakes potentially exposed to flooding by overflow are the greatest. It indicates areas subject to a low, medium or high probability of overflow flooding.
Indicator ID: FR_TRI_d
Mesh: ~100 m (depending on the level of probability)
Source: Georisques
Data processing: The data is uploaded in cartographic format to Georisques. A geometry repair mapping treatment is done first. Then, different mapping treatments make it possible to individualize the three levels of flood probability and to remove the overlaps between them.
Scope: Metropolitan France
​
Areas prone to runoff flooding
Definition of the indicator: The territory at significant risk of flooding (TRI) by runoff is an area where the issues potentially exposed to flooding by runoff are the greatest. It indicates areas subject to a low, medium or high probability of runoff flooding.
Indicator ID: FR_TRI_r
Mesh: ~100 m (depending on the level of probability)
Source: Georisques
Data processing: The data is uploaded in cartographic format to Georisques. A geometry repair mapping process is done first. Then, different mapping process make it possible to individualize the three levels of flood probability and to remove the overlaps between them.
Scope: Metropolitan France
​
Hazard levels in risk prevention plans
Definition of the indicator: In municipalities covered by a flood risk prevention plan, this zoning corresponds to a graduation according to the level of the hazard (from 'None' to 'Very high +') at which the hazard area is exposed. The allocation of a hazard level at a given point in the territory takes into account the probability of occurrence of the dangerous phenomenon and its degree of intensity. Areas covered by a flood risk prevention plan but where precise zoning is not available are considered as "Data not available".
Indicator ID: FR_PPRi_alea
Mesh: ~100 m (depending on the level of risk)
Source: Georisques
Data processing: The data is uploaded in cartographic format to Georisques. A geometry repair mapping process is done first. Then, different mapping processes make it possible to individualize the different levels of flood risk and to remove the overlaps between them, and finally to combine this information with the municipal coverage in Flood Risk Prevention Plans.
Scope: Metropolitan France
​
Definition of the indicator: The rate of soil sealing represents the percentage of impermeable surface (from 0 to 100) on 20m grids. This indicator is available for 50 French urban areas.
Indicator identifier: Fr_imper
Mesh: ~20m
Source : High resolution layers produced by Copernicus
Data processing: The high resolution layers were downloaded in raster format for the whole of France. After vectorisation of the data, they were cut around French urban areas. The coverage chosen is equivalent to that of the UHI indicator used for the heat hazard. In the case of cities that are not covered by the UHI model but are important in France (Marseille, Strasbourg, Rennes, etc.), the division was made according to the extent of the given municipality as well as the neighbouring municipalities (according to the continuity of the urban coverage in view of the LCZ (Local Climate Zone) data).
Scope: 50 French cities
In order to obtain a single exposure index revealing the climatic risk situation of a building in an area, the previous indicators have been combined under the following formula:
The K coefficients are established according to the following different cases:
- Case 1: The municipality in which the building is located is not covered by a flood PPR, the building is not located in the zoning of a territory at risk of flooding by overflow or runoff, and the difference of extreme daily precipitation is greater than 0.
​
​
​
- Case 2: The municipality in which the building is located is not covered by a flood PPR, the building is not located in the zoning of a territory at risk of flooding by overflow or runoff, and the deviation from extreme daily precipitation is less than 0.
​
​
​
- Case 3: The municipality in which the building is located is covered by a PPR flood or the building is located in the zoning of a territory at risk of flooding by overflow or runoff, and the difference in extreme daily precipitation is greater than 0.
​
​
​
- Case 4:
The municipality in which the building is located is covered by a flood PPR or the building is located in the zoning of a territory at risk of flooding by overflow or runoff, and the difference in extreme daily precipitation is less than 0.
In all cases, the K coefficients for precipitation (ECARTPQ99) takes into account the maximum encountered for this indicator, over the whole of France from 2020 to 2100 for the 3 scenarios. This makes it possible to put the risk in a specific location into perspective in relation to the risk existing in the whole of France.
​
The calculation of the initial risk is based on the historical risk (Rinitial). For this, the zoning of the risk prevention plans, the zoning of areas at risk of flooding and the risk of rising groundwater are taken into account. Risk levels are converted from their initial values to 0 to 4 according to the table below. The maximum of these three indicators is then kept.
​
​
​
​
​
​
​
​
​
​
​
​
​
​
Thus, this formula accounts for the initial known risk in the area (according to historical information on the risks and the experience of disaster in the area), which is weighted according to the variable components linked to the urban space (the rate of soil sealing) or climate change (difference in extreme daily precipitation).
The exposure reliability index is assigned as follows:
5/5 Models used in the IPCC report empirically verified
4/5 Models used in the IPCC report
3/5 Other models - Very reliable
2/5 Other models - Moderately reliable
1/5 Other models - Unreliable
​
RAINFALL AND FLOODS HAZARD
In order to calculate the vulnerability of buildings to the “Rainfall and floods” hazard, a certain amount of information is necessary. In order to collect them, a form is available to complete the characteristics of your project.
​
If no information is passed, the vulnerability defaults to 100%, with zero reliability.
The building vulnerability matrix for the “Rainfall and flood” hazard is available here for download in Excel format. This allows you to know the intermediate steps of the calculations performed in R4RE.
The vulnerability ranges between 0% and 100%. The greater the vulnerability, the more the building is subject to adaptation.
The vulnerability reliability index is calculated from the number of questions answered compared to the total number of questions. It varies from 0 to 5.
​