Brief communication: How well are Londoners prepared for flooding? An assessment of risk mitigation actions and a pilot comparison of perceived and modelled flood likelihood

Russell, Andrew; Khosa, Prarthna Kaur

doi:10.5194/egusphere-2026-3820

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https://doi.org/10.5194/egusphere-2026-3820

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14 Jul 2026

| 14 Jul 2026

Status: this preprint is open for discussion and under review for Natural Hazards and Earth System Sciences (NHESS).

Brief communication: How well are Londoners prepared for flooding? An assessment of risk mitigation actions and a pilot comparison of perceived and modelled flood likelihood

Andrew Russell and Prarthna Kaur Khosa

Abstract. Surface water flooding probability in London is high but little is known about how aware Londoners are of their exposure. 183 online survey responses showed large differences between perceived flood likelihood and modelled flood probability for respondents’ homes (where the latter could be confidently determined - full addresses cannot be collected due to ethical constraints, which limited sample size and representativeness): 54.6 % overestimated their flood likelihood, 19.7 % underestimated, and 25.7 % were accurate. Residents in high flood probability locations underestimated their exposure. Self-reported flood probability knowledge increased perception accuracy. Climate change concern was linked to flood probability overestimation and implementation of risk mitigation actions.

Received: 28 Jun 2026 – Discussion started: 14 Jul 2026

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Andrew Russell and Prarthna Kaur Khosa

Status: open (until 25 Aug 2026)

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RC1:
'Comment on egusphere-2026-3820', Milad Basirifard, 14 Jul 2026 reply
The principal percentages appear to be mathematically incorrect. This is the most serious problem. Table 1 states that the comparison sample contains 183 respondents, including 30 who answered “unsure.” Table 2 nevertheless also totals 183 observations while claiming to classify respondents as underestimating, accurately estimating, or overestimating flood probability. The reported counts are 36 underestimated, 47 accurate, and 100 overestimated, which sum to 183. An “unsure” response cannot logically be assigned an ordered difference of one or more probability bands. The numbers strongly suggest that the 30 “unsure” respondents may have been added to the underestimation group: Table 1 implies only approximately six genuine underestimators, while Table 2 reports 36. Moreover, the diagonal percentages in Table 1 appear to produce approximately 45 accurate responses, not 47.

Respondents were asked about the general flood risk level where they live, without specifying the source of flooding. However, the authors compare these answers specifically against surface-water flood probability, selected because it was reportedly the highest modelled probability for the retained addresses.

The government tool requires a full address because flood probability can vary among properties within a postcode. The authors did not collect addresses and instead retained postcodes in which at least 75% of addresses shared a flood category. This does not establish the flood category of a particular respondent’s property. Up to 25% of addresses may still belong to another category, and no evidence is presented showing the expected individual-level classification error. The 75% threshold is arbitrary, and there is no sensitivity analysis using thresholds such as 80%, 90%, or 100%.

The manuscript highlights that all respondents in the medium- or high-probability categories underestimated their exposure. Yet this claim is based on one medium-probability and four high-probability respondents. Five observations cannot support statements about residents in high flood probability locations, as presented in the abstract. The uncertainty is enormous, and the finding could easily be a sampling accident. It should not appear as a principal conclusion. At most, it may be reported as an anecdotal pilot observation requiring confirmation in a risk-stratified sample.

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Citation: https://doi.org/10.5194/egusphere-2026-3820-RC1

Andrew Russell and Prarthna Kaur Khosa

Supplement

https://doi.org/10.5194/egusphere-2026-3820-supplement

Andrew Russell and Prarthna Kaur Khosa

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Latest update: 14 Jul 2026

Short summary

As our climate changes and flooding becomes more likely, particularly in big cities, we need to know how accurately people assess the probability of their homes flooding and what actions they are taking to respond to that. In this research, we surveyed people in London to work out how well their assessments of flood potential align with official assessments and what people are doing about it. We find that most people overestimate their exposure but those at most risk underestimate it.