the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 14 Jul 2025
An assessment of multiple variables predicting the psychological effects of flooding: Case study in Peninsular Malaysia
Abstract. Floods are among the most disastrous environmental hazards, causing devastating tangible and intangible impacts. The psychological impact, which can be classified as intangible damage, is an important aspect of human’s well- being. The psychological impact of flooding has begun to receive attention in recent years, but the complexity of measuring it makes it less attractive to be considered in actual flood damage and risk studies. The present study seeks to evaluate the psychological impact of flooding experienced by households and business premises and the different factors that could be the determining variables of the psychological impact. A total of 217 respondents have participated in the empirical face-to-face survey conducted in different vulnerable places in Peninsular Malaysia. Through the willingness-to-pay (WTP) method, only 107 and 34 respondents from residential and business premises, respectively, expressed their agreement to spend on flood risk reduction efforts. The study found that flood durations and family sizes are statistically significant contributors to intangible damages for households, reflecting the intangible damages to residential sector. The results suggest a greater investment to support affected people’s welfare by improving community awareness and shelter facilities. These will enhance risk management efforts and reduce the psychological impacts to people at risk of flooding. The findings also revealed a key challenge: the inability to reliably infer intangible flood damages for business sectors through empirical evidence.
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Status: final response (author comments only)
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RC1: 'Comment on egusphere-2025-2917', Anonymous Referee #1, 15 Jul 2025
I appreciate the authors' submission and found the paper to be of significant interest. My comments below are intended to assist in further refining the manuscript:
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The paper states the application of the Contingent Valuation Method (CVM) for valuing intangible impacts, which is theoretically sound given its ability as a stated preference method to holistically capture intangible impacts compared to revealed preference methods. However, I find the methodological description to be insufficiently robust. While variations in the CVM approach exist, the guidelines established by Arrow et al. (1993) have been highly influential in shaping key aspects of CVM studies. For instance, the paper lacks crucial details such as whether a dichotomous choice Willingness-To-Pay (WTP) question was employed, the range of random bid values presented (if applicable) to cover the distribution of values, the precise wording of the WTP question, and the payment vehicle through which respondents were expected to contribute. While I do not seek to prescribe a specific approach, the absence of this information makes replication of the CVM methodology impossible. I am left to assume that respondents were simply asked to provide a hypothetical WTP value. While all stated preference studies are susceptible to hypothetical bias, the unguided elicitation of a raw value from respondents represents the weakest form of CVM.
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Given the pivotal role of the WTP question in the calculation of intangible damages, it would be beneficial to include an analysis of why respondents declined to answer the WTP question or rejected the offered bid values. Understanding these reasons could provide valuable insights into the valuation process.
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The focus on intangible damage raises a conceptual question regarding its comparability across businesses and individuals. It appears that the study may primarily be examining the psychological intangible damage experienced by the respondent. I note the absence of a table indicating the proportion of Small and Medium-sized Enterprises (SMEs) among business owners. It is conceivable that for many smaller businesses, the business entity and the owner are practically indistinguishable. Rather than distinct categories of damage, it seems the differentiation between businesses and individuals might lie in the pathway through which the damage manifests.
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Line 99: The sentence appears to be incomplete.
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The flood histories of the case study areas are only briefly mentioned. Expanding on the frequency and magnitude of significant flood events within the last 10 years would greatly enrich the background context for potential respondents and their experiences.
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Line 235: Clarification is needed. Is it that individuals are inherently more susceptible to flooding, or is it that, when focusing on intangible damage, there is simply greater scope for experiencing intangible losses when a flood impacts one's home compared to one's place of business?
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A clear delineation between intangible and tangible damages is essential. The WTP question (at least as I infer it from the context) likely conflates both tangible and intangible damages with an individual's perceived budget for implementing risk reduction measures. For example, an individual might experience significant psychological distress and heightened anxiety post-flood, yet only be willing to spend $5,000 on flood defenses due to budget constraints. This $5,000, while a personal maximum, may still represent a lower bound on their perceived total flood damage. This point seems to be echoed in the statement that poorer respondents report less flood damage due to having fewer physical assets. However, there is no inherent reason why this principle should extend to the emotional or intangible damage suffered during a flood.
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Given that the survey was conducted post-flood, significant variations in recovery rates would be expected. Therefore, why is it that the regression modeling/survey did not incorporate any variables related to the recovery process. Furthermore, access to recovery mechanisms is likely to intersect with several of the socio-demographic variables already included.
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I observed the absence of a regression analysis for the business observations. Am I correct in inferring from Table 4 that some form of variable reduction process was undertaken? Further clarification on this would be helpful.
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Overall, I am not entirely convinced by the paper's approach to calculating intangible damage. At best, the CVM, within the constraints of an individual's budget, provides a measure of their willingness to pay to reduce such damage. However, this is not synonymous with the actual intangible damage itself, although the two are undeniably related. Consequently, a more accurate title for the paper might be, "An Assessment of the Willingness to Pay for Flood Risk Reduction: A Case Study in Peninsular Malaysia," which, while still valuable, addresses a slightly less novel research question. Addressing this question would require a different framing of the paper, and which would open further questions about why the socio-psychological domain of variables and welfare with was not included in the paper (e.g., where are risk perceptions as someone who expects to be flooded again may have even larger intangible impacts because they are "stuck") given that psychological damage is psychological and will be driven by the interaction with other tangible and intangible factors.
Citation: https://doi.org/10.5194/egusphere-2025-2917-RC1 -
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RC2: 'Comment on egusphere-2025-2917', Anonymous Referee #2, 22 Jul 2025
This paper addresses an important issue in understanding the intangible impacts of flooding, an area that is often underrepresented in flood risk assessments, and I enjoyed reading this manuscript. Applying WTP to capture these impacts is a novel and potentially valuable contribution. However, the study primarily reiterates established correlations, and its results are limited by small sample sizes, particularly in business.
Overall concept: While the authors describe intangible damage as psychological distress, they do not adequately justify the use of WTP as a proxy for such impacts. WTP is traditionally applied to non-market goods, but using it to value mental health effects requires strong support. It assumes that WTP correlates with psychological damage, yet it is heavily influenced by other considerations, and so interpreting WTP as a direct measure is misleading. A clearer rationale and discussion of its limitations are needed. The lack of detail explaining the CVM, as mentioned by the other reviewer, undermines not only the validity of the WTP as a proxy for psychological impact.
Introduction: There need to be more citations, depth, and restructuring. It would benefit from an in-depth literature review; could you include recent work on flood resilience and mental health in SE Asia? Some claims in the introduction lack evidence.
Methods: The authors use regression models, but they do not justify the variable selection, and there is no discussion around the low R2 values. What unmeasured variables might explain the variance? The authors removed variables but gave no detail as to how they tested multicollinearity. The comparison of total damages is misleading without accounting for sample size differences. You should consider focusing on average damage values to make comparisons more meaningful. The paper does not account for the time elapsed since the flood events. When were the interviews done? If the study was done shortly after the floods, psychological effects might not yet be fully visible.
Discussion: The discussion section is overly descriptive, repeating findings without offering deeper analysis. For instance, the observation that B40 households report lower average intangible damages than T20 contradicts expectations, yet no explanation is offered. The finding that income is not a significant predictor is not examined for its implications. Rather than simply citing studies with similar or differing results, the authors should critically assess why the results agree or diverge. The authors should engage more critically with their data, exploring possible explanations and linking findings to concrete policy recommendations or planning strategies. There are sweeping statements and generalisations that are problematic.
Ethical framing: There needs to be a more ethical tone in the summarising of the results. The refusal to contribute does not equate to a lack of impact but may reflect structural constraints or emotional exhaustion or other factors. A bit more sensitivity in writing up these findings would be effective. Do you have any reflections on the ethics of monetising trauma?
Writing quality: The manuscript is weakened by poor sentence structure and grammar issues, which undermine the quality. There is a lot of repetition, Figs 3 and 4 are hard to interpret (lack of labelling and descriptive captions), and editing is strongly recommended.
Minor points: Instead of elderlies, elderly people should be used. There are some formatting issues. Some tables are hard to interpret such as lacking units. Parts of your results are in the methods part. See attached doc.
Please see the minor comments in the attached document.
Overall, this study addresses an important topic. However, it requires a more rigorous application and explanation of the CVM methodology, clearer justification for its use as a proxy for psychological impacts, and deeper engagement with contextual, policy, and ethical dimensions.
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RC3: 'Comment on egusphere-2025-2917', Anonymous Referee #3, 10 Aug 2025
The paper addresses an important aspect of flood risk assessment and management: psychological effects of flooding on affected people and how to integrate this in quantitative risk assessments. The paper presents a (small) dataset from Malaysia from 107 residents and 34 businesses, in which they applied a "willingness to pay" (WTP) approach to derive a monetary proxy for psychological effects of flooding. Regressions are used to explore relations between this dependent variable and other variables.
In line with the other two reviews I acknowledge the relevance of the topic, but I see similar weaknesses in the current presentation: the justification of the WTP approach and curcial details on its implementation in the questionnaire are widely missing. Therefore, it is hard to assess the overall quality of the study. However, the fact that only 141 out of 380 respondents answered the WTP question, reveals that there were difficulties with this approach which probably led to uncertain data. The authors should comment on this in much more detail. It remains unclear why only 217 out of 380 responses were valid at all and why so many refused to answer the WTP question. How do you assess the general validity of your data?
Further concerns are:
- In the introduction, several statements (see attached file) should be supported by references. Please add the relevant literature. Provide an overview of studies that have investigated psychological effects of flooding (also called: mental health effects or effects on well-being). Please use common risk terminology (e.g. exposure).
- Also add some more information on the processes and impacts of 2014-event in Malaysia.
- Clearly distinguish methods from results and clearly present your hypotheses at the end of the introduction (and not just in line 168/169; see my comments in the attachment). Please restructure the paper accordingly and avoid repetitions.
- Please provide some official statistics on socio-economics of the population in the study area and compare the numbers with the findings from your dataset.
- Due to the small size of the sub-samples in the figures 3 and 4, some bins should be merged.
- In fact, I do like the suggestion in the first review on how to frame the work in a different way and how to change the title.
- Please have a look at the attached file.
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