Data on surface water bodies like rivers, dams, reservoirs, and related  flow characteristics, along with assessments for water risks, stress, and flood risk. 

freshwater

Freshwater

Data related to water scarcity, water quality, flood risk, and water stress.

water-risks

Water Risks

### Overview  
  
Riverine flood risk measures the percentage of the population expected to be affected by riverine flooding in an average year, accounting for existing flood-protection standards. Higher values indicate that a greater proportion of the population is expected to be impacted by riverine floods on average. These values were then converted into risk scores based on the thresholds defined in the methodology. These risk scores range from low (<0.1%) to extremely high (>1%).

  
  
Flood risk was assessed using hazard (inundation caused by river overflow), exposure (population in flood zone), and vulnerability. The existing level of flood protection was also incorporated into the risk calculation. It is important to note that this indicator represents flood risk not in terms of maximum possible impact but rather as average annual impact. The impacts from infrequent, extreme flood years were averaged with more common, less newsworthy flood years to produce the “expected annual affected population.”  Values are available per sub-basin (HydroBASIN level 6). 
  
  
### Methodology  
  
Data on the population impacted by riverine floods were provided by Aqueduct Floods (Ward et al. forthcoming). Flood risk was simulated using a cascade of models within the Global Flood Risk with IMAGE Scenarios (GLOFRIS) modeling framework [(Winsemius et al. 2013)](https://doi.org/10.5194/hess-17-1871-2013). Riverine hazard maps were derived using PCR-GLOBWB 2 inputs from 1960-1999. The riverine flood hazard is represented by inundation maps showing the flood extent and depth for floods of several return periods (2, 5, 10, 25, 50, 100, 250, 500, and 1000 years) at a horizontal resolution of 5’ x 5’ (regridded to 30” x 30”). Exposure is represented by gridded maps of 2010 population count per cell at a horizontal resolution of 30” x 30". Vulnerability is represented as a binary condition: people are either affected or they are not. Estimates of flood protection standards come from the [FLOPROS model](https://doi.org/10.5194/nhess-16-1049-2016). 

  
  
The expected annual affected population was calculated using a risk curve [(Meyer et al. 2009)](https://doi.org/10.1897/IEAM_2008-031.1). To create the curve, the return periods were first converted into probabilities (i.e., 1/return period) and then plotted on the x-axis against the impacted population. Next, flood protection (return year converted to probability) was added to the graph as a vertical line. All impacts that fell to the right of the flood protection line (i.e., impacted by smaller floods) were assumed to be protected against floods and were removed from the calculation. The expected annual affected population was calculated by integrating the area under the curve to the left of the flood protection line.

  
  
The expected annual affected population was divided by total population to calculate the percent of the population expected to be affected annually by riverine floods.

  
  
Finally, raw riverine flood risk values were converted to risk scores between 0 and 5, based on quantiles. These scores were placed into categories indicating how high the risk for this indicator is. The thresholds for raw riverine flood risk values and the corresponding risk scores that were used in each category are defined below as Risk Category (Risk Scores): Raw Value Thresholds.

- Low (0-1): < 0 to 1 in 1,000 people
- Low to medium (1-2): 1 in 1,000 to 2 in 1,000 people
- Medium to high (2-3): 2 in 1,000 to 6 in 1,000 people
- High (3-4): 6 in 1,000 people to 1 in 100 people
- Extremely high (4-5): > 1 in 100 people

  
  
For the full documentation, please see the source [methodology](https://www.wri.org/publication/aqueduct-30).  
  
### Additional Information  
  
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### Disclaimer  
  
Excerpts of this description page were taken from the source metadata.

PBL Netherlands Environmental Assessment Agency (PBL)

Riverine Flood Risk, Aqueduct 3.0

wat-055-aqueduct-riverine-flood-risk-rw

water-peace-security

Water, Peace & Security

2010 Riverine Flood Risk

Measures the percentage of the population expected to be affected by riverine flooding in an average year

Water, Peace & Security

Aqueduct Riverine Flood Risk

2010 Riverine Flood Risk