Coastal Processes, Hazards, and Society

Goals and Objectives


Goals and Objectives

Learning Objectives

By the end of this module, students should be able to:

  • analyze real-world data on the global distribution of cities identified as most vulnerable to coastal flooding;
  • consider the multiple variables that determine the ranking of these cities in the present and future;
  • use geospatial skills with Google Earth to explore and compile data for a variety of coastal communities at risk from coastal flooding.

Module 1 Roadmap

Module 1 Roadmap
-- Assignment
To Read In addition to reading all of the required materials here on the course web site, before you begin working through this module, please listen to/read the following required readings to build some required background knowledge on sea level rise predictions and future changes in storm intensity.
Click for a transcript of the Podcast: Got Science? Episode 36: Coastal Homes and Properties at Risk: Sea Level Rise, Flooding, and Inundation

As we’re recording today, it’s just past the first official day of summer. I happen to live year-round in a beach town here in Massachusetts—so for me, that means it’s tourist season. They’ve arrived and they’re everywhere!

Some folks come to spend the summer in my town, where they have houses that may have been handed down in their families for generations. Some folks come for a few weeks at a time and stay in a summer rental or the local hotel, steps from the water. And some folks make the drive down from Boston to lie out on the beach for the day, and grab a bite to eat.

So many people have fond memories of spending their long summer days in my town. I do, too, of course… since I live there by choice. And so much of our local economy depends on tourism, and the revenue generated by the people who visit us, and spend money at our businesses.

So I’ll be honest: I kind of didn’t want to have the conversation that follows with today’s guest, my colleague, Dr. Rachel Cleetus. It’s not that I don’t want to talk to Rachel! She’s fabulous. But she’s an economist and a sea level rise specialist here at the Union of Concerned Scientists. And her team has just released a new report on coastal real estate…and how sea level rise is a serious and unaccounted-for threat to millions of dollars’ worth of homes and businesses located in seaside cities and towns like mine.

Rachel is our lead economist and policy director, which means she can clearly see how rising seas can spell real financial trouble for coastal communities. She joined us to talk about the implications of this new research, what it means for towns like mine and the people who live there…and what she would do differently if she were crowned Queen of Science-Based Sea Level Rise Policy.

Colleen: Rachel, thanks for joining me on the Got Science? Podcast.

Rachel: Thank you so much for having me, Colleen.

Colleen: So you're one of the authors on a report that was recently released titled "Underwater: Rising Seas, Chronic Floods, and the Implications for U.S. Coastal Real Estate." So tell me about the analysis and who you're trying to reach.

Rachel: Well, with this analysis, what we were trying to do was look at the risk to coastal properties all along the lower 48 states of the U.S. from chronic inundation. And this is regular high-tide flooding that's getting worse because of sea level rise. We're seeing high-tides get higher reach further inland and this is putting a lot of property and people in harm's way.

Colleen: And what's the time span that you're looking at?

Rachel: With this analysis, we're looking as near as 2045, within the lifetime of a 30-year mortgage issued today. And then we go out to the end of this century, looking at this risk of chronic inundation which we define as 26 times per year or more of high-tide flooding.

Colleen: So this is not from major storms, this is happening throughout the year on a regular basis, places are flooding?

Rachel: The reality is, even in the absence of storms, this type of high-tide flooding is getting worse because of accelerating sea level rise.

Colleen: So, how did you approach the analysis? What data did you use?

Rachel: We started with data from NOAA which basically looks at sea level rise today and projections out to 2100. We localized these sea level rise projections because in many places along the east and gulf coast of the U.S. we're actually seeing higher and faster rates of sea level rise because of other local factors like land subsidence. And onto this data, we intersected a property dataset coming from Zillow to look at the property at risk from high-tide flooding.

Colleen: So you can're actually looking at a community and saying, by 2045, X number of houses will be underwater or really no longer in livable condition?

Rachel: By bringing together this data from NOAA on sea level rise and the property data from Zillow, we are able to tell at the zip code level how many properties, the value of properties, and the tax base those properties represent that are at risk from chronic inundation.

Colleen: So who are you really trying to reach with this report?

Rachel: Our aim here with this research is really to inform people about what the science is telling us about this looming risk that's flying under the radar frankly, at this point, in many parts of the U.S. coast. So we want people to be educated to make decisions about key things like the homes they own which are often people's single biggest financial asset, based on the best available information about the kind of risk that's coming our way because of climate change and sea level rise.

Colleen: Let’s sort of zoom in on the map. What were some of the communities, cities, areas that are going to see the biggest impact?

Rachel: Well, with this research, what we found was that there are some parts of the country, particularly in places in Florida, New Jersey, California, and New York that are very highly-exposed in terms of the numbers of property and the value of that property that is at risk. That said, there are many other places where, in dollar terms, the value may not be high, but these are still people's single biggest asset. So ordinary working class communities, low-income communities where the homes may not be super expensive, but these are people's only homes. And there are many, many of those types of communities as well in New Jersey, North Carolina, Massachusetts, Louisiana, all around the country, many communities that might see a significant portion of their housing stock at risk as well as their local property tax base.

Colleen: Many of the communities at risk have poverty levels above the national average. So tell me about those communities.

Rachel: There are many communities that are facing not just the physical risk from sea level rise, but also additional socio-economic challenges that mean they have fewer resources to cope with the kind of tidal flooding that we have identified in our research. In fact, we found that there were many places around the country that were at risk of losing 10% or more of their housing stock. And nearly 40% of these currently have poverty levels above the national average. These are places, for example, in coastal Louisiana like Terrebonne Parish, there are places along the eastern shore of Maryland in New Jersey, in North Carolina. And these places require additional targeted attention to make sure that they don't get left behind as we prepare for a future of sea level rise. We also looked at places which have a high number of elderly folk who live on fixed incomes, who also have a lot of their assets tied up in their home value, and would face significant financial challenges if their homes were to lose value. And then we looked at a lot of blue-collar communities around the country in Massachusetts, in New Jersey. Many other places where frankly, these homes are valued below the median value of their states. In Massachusetts, for example, we looked at places in Revere, Saugus, and Winthrop, where communities that we're seeing hundreds of homes at risk. Many of these homes valued at 60% or lower below the state median. So these are ordinary working class people's homes. Again, a lot of their financial well-being tied up in the value of these homes.

Colleen: So you're saying there are dire consequences to go around, homeowners are at risk, communities, the real estate market, investors, bankers, insurers, developers. How did we get into this situation? Haven't we known that this was coming?

Rachel: Well, we are a coastal nation. And our coasts have long had a draw for people, you know. We have a lot of our economic centers, places people love to vacation, places people have lived in for generations along our coastline. But the reality is now these coasts are threatened by sea level rise. And unfortunately, this risk is being masked because of shortsighted policies, shortsighted investment horizons in the marketplace that are, unfortunately, masking the risk but also putting more people and property in harm's way. So we have to do a better job making sure that these policies and market incentives serve us better going forward that people are informed of these risks and can take protective measures to help ameliorate it to the extent possible. That said, you know, what's important to recognize is while those risks starts out as a risk to individual homeowners or owners of commercial property, that's just the beginning. It starts to reverberate out from that point to communities and the wider economy because, of course, as homes lose value, the property tax base can get eroded. That means that communities have a harder time funding critical local services and infrastructure. And then it also affects investors, coastal real estate investors, banks who have made mortgage loans on these homes that are losing value. And in this way, it can really trigger a much wider economic crisis than just in an individual place where this risk is unfolding.

Colleen: So I heard you talk about risk perception catching up with reality, and you said and I'm going to quote you now, "Unfortunately, in the years ahead, many coastal communities will face declining property values as risk perceptions catch up with reality. In contrast with previous housing market crashes, values of properties chronically inundated due to sea level rise are unlikely to recover and will only continue to go further underwater," which is what we were just talking about that long view. So I live in a small seaside town south of Boston, where risk perception has not caught up with reality. I continue to see houses being built on stilts, on very narrow strips of land. I see real estate agents selling houses in flood-prone areas every day. It gives the impression that the town is doing business as usual. And I'm wondering where a community living on that edge would start the process, where do we begin?

Rachel: Well, the first thing is I think communities need to be aware of their risk. They need to be proactive in finding out what these risks are gonna look like for them. But then I think this is actually a national imperative. We shouldn't be leaving individual communities to try to figure this out on their own because most don't have the resources or the wherewithal to take the protective measures they need to take, or even to assess their risks and options. And that's where it's really critical that the federal government play a leadership role in providing the resources, the policies, the tools, and data that people need to help protect themselves. So what we hope is that there will be a call from the local to the national to galvanize that kind of effort. One really interesting thing as we did this research, we also spoke to a lot of financial sector and market experts, including folks like S&P Global Ratings, Breckinridge Capital Advisors. These are folks who deal with real estate and market signals every day, that's their business. And what was striking to us is to a person, they all agree that this risk was real significant and largely unaccounted for in the market today because of the short-term investment horizons. And they all pointed out that the market will eventually correct. Unfortunately for many coastal communities, this is not gonna fly under the radar forever and there is going to be a correction. And it will be harsh for some communities if we don't get out ahead of this challenge.

Colleen: Yeah. A lot of what I see happening in my community are adaptation measures. We're building a bigger seawall. And they feel like band-aid fixes. It feels like there needs to be a much longer-term solution.

Rachel: Sure, communities are scrambling to do what they can with the resources and the information that they have. And unfortunately, in many cases, these are solutions that will have a limited effectiveness as sea level rise accelerates and tidal flooding gets worse. So we have to be really clear right about using the time we have left wisely, making sure that the investments we're making will serve people in the long run, will truly be protective of people and their financial well-being. And that means that we have to look at some of these defensive measures and recognize that they do have limitations. They may not serve us well in the long run. They're very expensive and will need to be maintained. So they have limited effectiveness.

Colleen: If you were in charge of federal policy on coastal resilience management, what are the first items on your to-do list?

Rachel: So the first thing that we need to do is update our flood risk maps, which are woefully inadequate. They just reflect current conditions, don't tell us anything about this future risk that's coming our way. These maps have been severely underfunded by Congress. We need to put the money into updating these maps so people have the information they need to protect themselves. The next thing I would do is instead of investing just in the aftermath of coastal disasters, we need to be proactive and get out ahead and invest in resilience measures ahead of time.

Colleen: So what do you mean when you say resilience measure?

Rachel: So there are a variety of ways, depending on the location and how exposed it is to flood risks, depending on the topography and how developed the area is that communities can take to mitigate against flood risk. There are things that individual homeowners can do in terms of elevating and flood-proofing their homes. There are things communities can do in terms of making sure that they protect their wetlands, that they leave open space that can flood regularly and not expose property to that flooding. And then, there are, obviously, measures we can take at the local and state level around building and zoning regulations. And then right up to the federal level in terms of providing the policies and resources communities need to take make these investments in flood-proofing measures. And then one really important aspect of giving people options to deal with this risk is to provide home buyout programs, voluntary home buyout programs in some high risk areas so that people don’t face the stark choice of staying in place in harm’s way or losing all of their financial assets. Home buyout programs can play an important role in helping people move away from these high risk areas. And then finally, out national flood insurance program, while a vital program, is unfortunately serving to subsidize living in some of the high risk places in the flood plain. We’ve got to reform this program, congress has an opportunity as a program comes up for reauthorization at the end of July this year, to ensure that some reforms are instituted that can help this program build resilience in the flood plain going forward.


Colleen: So what...imagine a dear friend of yours whom you haven't spoken with in a while calls you up out of the blue to tell you that she's found a charming house right on the water in, say, the outer banks of North Carolina and she's ready to buy. What would you tell her?

Rachel: Well, one of the things I would advise her to do is go read a brochure that we have on our website that is aimed at home buyers to educate them to ask certain questions before they make a home purchase. And these are questions to help assess the risk of chronic flooding to the neighborhood, to the home, to critical infrastructure in that neighborhood. Because all of these things really matter for the future value of the home. Most of us when we buy a home we're taking out a 30-year mortgage, we hope that that home will retain its value, in fact, that its value will increase. That will perhaps be able to leave it to our children and grandchildren. So we are taking a long view in terms of the investment that we're making. That means we have to do our due diligence upfront, making sure that our investment is as secure as possible. So ask the right questions of your realtor, of your town planner, the person who does your home inspection. Make sure you know the history, not just of the home, but also of the neighborhood. Make sure you're consulting maps, flood risk maps, as well as our own mapping tool on our website, which shows at the zip code level, the way the risk of chronic inundation will play out over the course of the next decades.

Colleen: So, Rachel, let's say we're BFFs, and I'm a realtor, what would you be talking to me about? My livelihood is selling houses right now, I'm not thinking about the long term. So what would you say to me?

Rachel: Well, most realtors have the interests of their clients at heart. They are certainly in the business of making sure that houses get bought and sold, but they are interested in making sure that their clients' long-term interests are best served. And in this case what I would say is that realtors need to recognize that the flood risk maps that they might be familiar with that FEMA produces, don't reflect this risk of tidal flooding. So, if they want to represent the interest of a prospective buyer, they should probably dig in a little bit further or visit the neighborhood at high tide, see what kind of actual impacts the neighborhood is seeing. Ask questions of the town planner to find out, you know, are they making investments in defensive measures or other types of adaptation? Look around the neighborhood and see do streets get flooded, you know, do things like that happen. And at the end of the day, ask the prospective buyer what type of risk they're willing to bear. You know, for some people, they might be open to the idea for living near the seafront to put up with a little bit of this nuisance flooding, but they should be really clear-eyed about the long-term risks at stake. It's not an easy situation, by any means, for anybody who's up close, including realtors, but there are some important questions worth asking right now just given the risk we know.

Colleen: So, I wanna follow up on the flood risk maps. So, you did mention that earlier in our conversation, and those are FEMA maps. So, how accurate are those maps? And I ask because we recently got new maps in my town where they redrew the flood lines, and it caused quite an outcry in the community. In part, because some people thought that the maps were not accurate. And then, of course, other people when they're redrawn and they're right on the line or right inside, that means their insurance is gonna go up a lot. But what can you tell us about the maps?

Rachel: So, the FEMA Flood Risk maps are based on current conditions. They don't reflect future conditions, including risk from projected sea level rise, tidal flooding, and that type of thing. So to that extent, they're inadequate to represent the risk that we're describing in our research. What's more, Congress has for a long time underfunded FEMA to produce these maps. And so there have been long periods of time where the maps haven't been updated. And so then, when FEMA does go to update, it certainly causes sometimes a shock in a community to discover that "Oh, wow," in the intervening years their risk has increased considerably. I would say that the real need right now is for people to be aware of the risk. Whether that's tied immediately to insurance increases is a separate question, I think, to the extent that they are those increases need to be phased in so they're not too jarring to people. But for a risk awareness need, I think the maps need to be updated to reflect these types of tidal flooding risks, so that people who are making decisions now are aware of the risks. And a lot of decisions get based on those FEMA Flood Risk maps, not just insurance premiums, but a lot of times, infrastructure decisions, utilities, making decisions about where to locate critical pieces of the power grid, etc. So we really need to be thinking about how forward-looking these maps need to be so that people can be making the right investments.

Colleen: So, I'm gonna put another hat on. Now I'm gonna be a town manager. What do you feel the town manager should be doing?

Rachel: Well, like everybody else who's on the front lines of this risk, town managers need to be acutely aware of where their exposure is, where does flooding tend to happen, are they seeing it in particular neighborhoods, streets, are there measures that they could take to invest in flood-proofing? And, oftentimes, towns start to think about hard defenses, but this is a moment also, to be thinking about how to use natural ecosystem infrastructure defenses. So, preserving wetlands, preserving open space, making sure that you have enough permeable surfaces so that water can actually soak in. As opposed to hard pavement which tends to exacerbate flooding during high tides, and even during heavy rainfall. And then, I guess, town managers are part of those local voices that need to be raised up to the national level to ask for the resources they need to help plan, invest in adaptation measures, communicate the risk to their communities. All of this is expensive stuff that's hard for small towns to do.

Colleen: This is really important research and incredibly sobering. Have you seen any positive changes happening?

Rachel: Yes. The research is really sobering. I think for all of us on the team when we saw the numbers come in, the numbers of homes and all the people along the coastline who are exposed to this risk, it really was a weighty moment when we saw those results for the first time. I think the most important thing to remember is that we do still have choices. The two most important choices we have ahead of us is how to use the time that we have left available wisely to invest in resilience measures to help protect people along the coastline to the extent we can, and to make deep cuts in our carbon emissions because one important piece of our research results was that if we, with the global community, adhere to the long-term goals of the Paris Agreement and if land-based ice thaws is limited, we can actually avert 80% to 85% of the chronic inundation damage that we identified in our report. So that's really significant. Cutting our carbon emissions can help limit sea level rise. And that means by the end of the century, fewer people, fewer homes, will be exposed to this risk of chronic inundation.

Colleen: I do wanna mention the online map where you can look at different areas on the coast. You can zoom in and get all of this detailed information. But there's also a tab on that map that talks about properties that won't be affected if we take stronger measures now.

Rachel: Sure.

Colleen: Which is a little more helpful.

Rachel: Yes. We encourage you to explore our interactive web-based mapping tool like And with this tool, you can go right down to the zip code level to explore a community's exposure to tidal flooding 2045 out to 2100. There is also a tab where you can look at what we call the homes in the balance. And these are the homes that would be spared if we were to adhere to the goals of the Paris Agreement and land-based ice thaws is limited. So again, right down to the zip code level, you can go and explore the homes that would be spared under this scenario.

Colleen: Well, Rachel, thanks for taking some time out of your busy day to join me.

Rachel: Thank you. My pleasure.

Extra readings are clearly noted throughout the module and can be pursued as your time and interest allow.

To Do
  • Complete Module 1 Lab A (Discussion - includes personal introductions).
  • Complete Module 1 Lab B.
  • Begin work on Capstone Project Stage 1.


If you have any questions, please use the Canvas email tool to contact the instructor.