# About flood risk scores

Flood risk scores provide an immediate measure of the risk of loss from the flood peril at both the location level and the policy level.

Individual risks (buildings) are ranked by risk profile, and sorted into five risk score categories. Each category has two labels: a numeric label (0, 2, 4, 7, 9) and a letter label (A–D, F). 0 or A is the lowest risk and 9 or F is highest.

## How they're calculated

The Cytora Risk Engine assigns a flood risk score to a location based on Annual Damage Ratio (ADR) values for each postcode unit (e.g. EC1V 0LN), with four separate flood scores: river, surface water, coastal, combined. The ADR provides a measure of flood risk by combining hazard and vulnerability information, and is expressed as a proportion of the total sum insured.

All risk scores are normalized for sum insured or a proxy such as building size.

Jump to: About Cytora risk scores

# Location-level flood risk scores

The flood risk scores are based on a location’s ADR value using a logarithmic scale:

## Risk Score letter |
## Risk score number |
## Maximum ADR value |

A |
0 |
0.000001 |

B |
2 |
0.00001 |

C |
4 |
0.0001 |

D |
7 |
0.001 |

F |
9 |
0.01 |

If there is no ADR value for a location, its flood risk score is NULL.

# Policy-level flood risk scores

When there are multiple locations in a policy, the policy-level score summarises them. It can be used to quickly identify policies with low risk of loss from flood, or to flag policies containing one or more addresses at high risk.

To calculate the policy-level flood score, location-level risk scores are weighted according to Cytora's estimated loss cost - D/7 (and especially F/9) scores have a greater impact on the policy-level score than scores of A/0 and B/2.

Jump to: How the overall risk score is calculated

# About the Annual Damage Ratio

The ADR data is based upon marginal event sets of 10,000 years, specifically developed at each individual location. The model accounts for flood defences for river and coastal flood scores.

Where a location includes multiple buildings (e.g. a postcode unit), the resulting ADR is an average of the ADRs for all properties in the postcode. This gives the best possible estimate of annualised loss for properties where the location is given as full unit postcode and the property type is unknown.

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