Preparing for More Flooding

This post reports on the results of a survey of flooding experiences in my district and adds very modestly to our understanding of flooding as a public policy issue. In short, flooding is a widespread problem driven by a combination of predictable long-term climate change and by hyper-local storm and water flow dynamics. It can only be understood and addressed by a collaborative approach spanning all levels of government as well as private agencies.

The Survey

I circulated a survey on flooding experiences to my constituents by email. I sent three solicitations to my office email list of approximately 5000 people. 870 people responded between November 4 and November 9. The survey form and the complete results (anonymized by excluding personal comments and address data) appear at the end of this post.

• 43% of respondents reported some basement flooding.  In soliciting responses, we did emphasize that people should respond whether or not they experienced flooding. However, there is no way to be sure the survey is representative.   It does seem fair to infer that flooding is common.
• Unsurprisingly, the longer people stay in their home, the more likely they are to report flooding and flood-related losses.  Among those in their homes over 5 years, 45% reported some flooding and 25% reported some damages (although only 4% filed claims). 
• A majority of respondents were not expecting flooding when they moved into their home (73%).  Among the 73% not expecting flooding,
  • 65% experienced no flooding and 34% experienced flooding;
  • 79% experienced no losses, 18% minor flood related losses but did not file claims, and 3% filed flood damage claims. 
• 36% of residents had made successful efforts to control flooding, while 5% had experienced repeated flooding despite efforts.  
  • People experiencing overland flooding as opposed to seepage were more likely to report failed efforts to control flooding (21% as opposed to 11%).    
  • People who had made repeated unsuccessful efforts to control flooding were more likely to report flood related damages (77%). 
• Residents living within 200 feet of a stream or wetlands were only slightly more likely to report flooding than than those further away (47% vs 42%). 
• Perhaps surprisingly, residents living on a “steep” slope were more likely to report flooding than others (14% on steep vs. 8% on some slope and 8% on mostly flat). 
• Results by zip code appear below. Downtown Boston zip codes show as having lower flooding, but this may be due to apartment dwellers on upper floors not at risk for flooding. The survey did not break out types of dwelling.

Discussion

The main takeaways from the survey are

• flooding is frequent (experienced by as much as half of respondents in some areas);
• flooding leading to a flood damage claim is relatively rare (only 4%, even among long-term residents);
• there is no strong relationship between flood experience and obvious topographical features like slope or proximity streams or wetlands — flooding can happen anywhere.

These findings — that flooding can happen anywhere, but most likely will cause modest damage — are consistent with a recent sophisticated report from the MAPC that examined claims for flood damage. That report found that “Ninety-six percent of the disaster claims arose in areas outside of the FEMA Special Flood Hazard Areas . . ..” Additionally, Figure 8 of the report showed little difference in claim rates between areas near water or wetlands and areas not near water or wetlands.

In our study, only approximately 1 in 6 of our respondents who experienced damage filed damage claims. Since it is based on filed claims for damage, the MAPC report tends to select the more serious incidents. However, even within this more severe subset, the MAPC found that average damage estimates were only $1,942 and the average award was only $1,762.

One might tend to infer from these findings that flooding is widely dispersed, unpredictable, and modest in impact — in other words, that flooding is an issue does not lend itself to public policy intervention. However, there are certain locations that do experience higher flood risks.

I first began focusing on flood risk late one rainy night in May 1998 when, as a member of the Belmont Select Board, I visited a constituent who called about sewage welling up in his basement slop sink. With Cambridge and Arlington, we formed a tri-community working group on flooding issues and — thanks to state and municipal agencies who responded to the issues we identified — we were able to substantially reduce both basement sewage flooding in Belmont and overland flooding along the Alewife Brook. People around the Alewife Brook are now focused on further reducing sewage overflows into the Brook.

Flooding is only going to get more important as an issue. It’s no secret that governments across the world are failing to meet stated goals for greenhouse gas reduction. A recent report from the United Nations commented on the “massive gap between rhetoric and reality.” Weaning the world economy from fossil fuels has been harder than people hoped. At the same time, we have made great progress in reducing emissions and will likely continue to do so as green technology improves and becomes more competitive. Through continued innovation, we can expect the world economy eventually to reduce emissions, but we meanwhile need to prepare for some climate change.

A study that I sponsored (see framing language in Section 39 of Chapter 52 of the Acts of 2014 and funding language in line item 7100-0207 of Chapter 165 of the Acts of 2014) indicated that, in the lower basins of the Charles and Mystic Rivers, the climate-related risks from coastal storm surge are greater than the risks from increased precipitation. As a result, I’ve focused on better understanding the risks from coastal storm surge in those watersheds and have supported projects to address them. Recently, flooding further west in Massachusetts has highlighted the potential for other streams and rivers to rise very high during intense rain events.

Last year, working with the Charles River Watershed Association, I helped pass language requiring the state’s Secretary of Energy and Environmental Affairs to assess the state of our flood risk understanding. In August, the Secretary produced the required draft report. It’s an excellent and very factual document. It catalogs in a thoughtful way our flood risk assessment resources and also highlights efforts to improve and expand those resources. The recommendations in the document recognize that — especially away from the coast — flood risk assessment requires detailed local knowledge, and that state and national agencies cannot fully define the risks. The document contemplates development of a platform on which the state can characterize risks on a broad scale and other agencies — regional, local, and private — can fill in the details in a consistent way. The agency’s approach seems both ambitious and practical and I support it.

To my mind, the findings of the MAPC report and the current survey reinforce the wisdom of EoEEA’s approach in the following sense: They suggest that much flooding is driven by hyperlocal factors (down to the individual home level), reinforcing the importance of collaboration across agencies to develop a complete picture. Similarly, our responses to flood risk will span the range from large infrastructure projects at the state or regional level to efforts by individual residents to control the flow of water into and around their homes.

Resources

• Anonymized Survey Results (870 responses)
• Flood Risk Mapping Resource Assessment and Recommendations, August 2025, draft report — see also slide deck point overview of draft report.
• Resilient Coasts Initiative
• MAPC report on storm water flooding damage claims
• Flooding and climate resiliency posts on this site

Survey Form

NOTE: The form is no longer active. Retained here for the record.

Note the first comments below were posted on the survey form post, before the final publication of the survey results.