Coastal Processes, Hazards, and Society

Vulnerability's Three Dimensions Introduction


Vulnerability's Three Dimensions Introduction

Let’s break down the concept of vulnerability to a coastal hazard into its components.

What Exactly is Vulnerability?

In terms of social science and natural hazards, vulnerability can be thought of as a three-dimensional construct.

The three dimensions of vulnerability we will explore are exposure, sensitivity, and adaptive capacity.

  • Exposure is the degree to which people and the things they value could be affected or “touched” by coastal hazards.
  • Sensitivity is the degree to which they could be harmed by that exposure.
  • Adaptive Capacity is the degree to which the community could mitigate the potential for harm by taking action to reduce exposure or sensitivity. This can also be thought of as a measure of resilience. See below.

Take a few minutes to watch at least the first 4-5 minutes of this short video focusing on the immediate aftermath of Hurricane Katrina in New Orleans and coastal Mississippi.

Video: Hurricane Katrina Survivor Clung to Trees as House Fell Apart: Part 2 (8:32)

Click here for a transcript of the Hurricane Katrina Survivor Clung to Trees as House Fell Apart: Part 2

Narrator: In the chaos of the rescues, Serena Johnson found herself living a nightmare.

Serena: We went to, it was a Louis Armstrong Airport. And when you walked into the airport, you saw all this, like, it smelled like a hospital. Some people were passing there.

Narrator: Desperation and despair were already hard to bear. But on top of that, many of evacuees, like Serena, were separated from loved ones. Hurricane Katrina caused the largest and most abrupt displacement in US history.

Serena: People allows businesses, people lost homes that they work hard on.

Narrator: A million people in the Gulf Coast were uprooted, scattered across all 50 states. Unsure of how to find her father, Serena and her mother had no option but to evacuate without him. Soon they were airlifted from New Orleans with no idea where they were going, where her father was, or if he was even alive.

Serena: I remember like looking to my mom like, with tears in my eyes, it was like I lost everything.

Narrator: Including the city she called home. And while a devastated New Orleans was drowning in unmerciful floodwaters, just 57 miles away on the Mississippi coast, Katrina had also left a trail of unimaginable destruction. More than 60,000 homes were destroyed back on August 29, when the eye of the hurricane made landfall directly over Waveland Mississippi. There, deadly storm surges, nearly 30 feet high, exceeded everyone's worst-case predictions, leaving an entire community trapped. That's when Howard Oh Quinn spring into action. This video shows Howard fighting the storm. As roads turned into raging rivers, and cars were completely underwater, he pulled aboard anyone needing his help.

Howard: We're driving the boat down the highway. I mean I never expected that in 100 years. Wind was screaming like you never heard it before. Rain was coming down it was like needles hitting us. We just started hearing people hollering,  so we start picking up people. They were all strangers.

Narrator: A true life boat with 15 desperate people crammed into a vessel meant to hold only six.

Howard: I had to do something, I'm not gonna leave them there. People was hollering for help, help, you go help em. I was scared, but I wasn't gonna let everybody in that boat know I was scared because I'd had a panic attack.

Narrator: Soon he heard frantic screams coming from this house, which was almost totally submerged.

Betty Gillan: We couldn't get our door open to get out.

Narrator: Betty Gillan, 76 at the time, was trapped inside.

Howard: I jumped overboard. When I opened up the door and I put her and her son and his girlfriend in the boat.

Betty: it was very scary.

Narrator: Howard navigated the boat through two miles of treacherous water, finally reaching safety on a motel balcony just above the water level.

Betty: He saved my life. He was like a little cloud come down from heaven, just to see me. I love ya Howard.

Howard: I love you too.

Narrator: Strangers before Katrina, now lifelong friends.

Howard: I mean they called me a hero, but everybody was a hero that made it out of that storm.

Narrator: For one woman we met in nearby Pass Christian, my hometown, there was no hero to rescue her. She's been silent about her story until now.

Diane Brugger: I was incredulous. I just couldn't imagine it. We thought we were safe

Narrator: Diane and Tony Brugger did not evacuate from Harbor Oaks, the historic inn they had lovingly restored. They believed it's 33-foot elevation was well above the predicted 25-foot storm surge.

Diane: It was supposed to be going towards New Orleans.

News Reporter: The track of the storm has shifted to the east.

News Reporter 2: Capable of producing a tornado seven miles southeast of Pass Christiana.

Narrator: The Brugger's took refuge on the top floor of their inn.

Diane: We saw the water coming, the cars and floating, and everything, and the water was almost up to scenic drive. And it was like, oh this is serious.

Narrator: News stations around the world covered the storm, reaching out to eyewitnesses who still had phone service. At daybreak, a Canadian news anchor spoke to Tony Brugger.

Tony Brugger: We had a couple of windows we weren't able to get to from the outside. They've already broken, so we're gonna try and board them up from the inside.

Narrator: He had no idea what was coming. One block away, police captured video of an alarming sight.

Policeman: That's Sergeant Michael Ali's patrol car.

Narrator: And as the waters continued to rise, tornadoes touched down in Mississippi, one of which hit the Brugger's full-on.

Diane: We were sitting in the, sitting on the bed, and the dogs were just going crazy, and the house you'd feel it sort of well you know, like lift up like a boat, and then settle back, and lift up like a boat. And we just looked at each other and I saw a weird acceptance in his eyes that really unnerved me. He almost was acknowledging that this was it. And I understood it, but I didn't accept it. But we said nothing. We just held hands and just looked at each other. And then when the house went up and then it didn't quite go right back down the way it was supposed to, and we all got up and then that's when the walls fell away and the ceiling came down. Then it just covered him.

Narrator: The house literally just started breaking apart.

Diane: It just sort of flattened out into like just a field of debris. Tony, when part of the ceiling came down, it caught his head and just took him right under.

Narrator: Somehow Diane survived.

Diane: The only thing I remember is the trees, there were two together, and I had a foot in one and a foot in the other tree. It was all just, hang on.

Narrator: She clung to the tree limbs for six hours until the violent storm subsided and she was rescued. Having lost the love of her life, her home, and her communty,  how could she possibly find the strength to carry on.

Narrator: A little later, how Diane discovers that determination. The amazing reinvention of a life. Also, a saint comes marching in.

Man: I needed somebody to believe in me just as much as New Orleans needed someone to believe in them.

Narrator: How Drew Brees and football win back the joy.

Knowledge Check Point

People and Things they Value

What is meant by the expression “people and things they value”?

This expression not only refers directly to people’s lives, livelihoods, and things of economic value, but also to places and to cultural, spiritual, and personal values. Also included are critical physical infrastructures such as police, emergency, and health services buildings, communication and transportation networks, public utilities, and schools, and daycare centers. It also refers to social infrastructures such as extended families, neighborhood watch groups, fraternal organizations, and more. The expression even includes such social factors as economic growth rates and economic vitality.

A community may be highly vulnerable to a low impact coastal hazard because of high sensitivity or low adaptive capacity – for example, a densely populated, impoverished neighborhood built on a low-lying shoreline could be easily inundated with a minimal flood from storm surge or tsunami and, due to the challenges imposed by poverty, they have great difficulty recovering from this event.

Another community can have a lower vulnerability to even high-impact coastal hazards because of low sensitivity or high adaptive capacity – for example, a wealthy tourist destination built to withstand flooding from storm surge may suffer a temporary setback when hit by a major hurricane but would be more likely to have the resources to rebuild than a low-income neighborhood would.

Therefore, coastal hazards can result in highly variable impacts because of these variations in vulnerability in time and space.

Disadvantaged groups of people are inherently more vulnerable to coastal hazards than others. The poor, the very old or very young, the sick, and the physically or mentally challenged are often vulnerable. Those lower educational attainment, or non-native speakers, are also often more vulnerable than native language-speaking people with higher levels of education. In the U.S., communities of color in coastal settings are often highly vulnerable, for example, this was true in New Orleans during Katrina and Puerto Rico during Maria. Vulnerable people may fit into more than one group. For example, the most vulnerable of a community could possibly be the minority, elderly, non-native speaking women.


What is Risk? Risk is the result of interaction between the components of the hazard and the vulnerability of the place that is impacted. Residents of a particular coastal community may weigh the risks of staying there versus relocating, or a person considering purchasing a house in a coastal community would definitely need to think about the risk to the property and his or her family and possessions. As we considered in our first exercise in Module 1, insurance companies account for all components of risk when determining insurance coverage. As the risk of devastating hurricanes has increased in the last decade, premiums have risen drastically in places such as South Florida. Below is a simple diagram summarizing the relationships between vulnerability, hazards, and risk.

Risk examples are obviously not restricted to coastal hazards. The descriptions above can be applied to other risks, such as serious illness during the COVID-19 epidemic. The risks of getting severely ill or dying vary greatly among different groups in a community, so that the elderly, those with underlying health conditions, and those living in group settings are at greater risk of severe illness from a COVID-19 infection than those who do not fit those demographics. Like other hazards, the disease has disproportionally affected minorities who tend to be poor and have more limited access to quality health care, so are more likely to suffer untreated underlying health conditions like high blood pressure and diabetes.

Frequency and intensity of hazard, paired with exposure, sensitivity, and resilience as they relate to vulnerability, contribute to risk.
Diagram illustrating the connections between hazard, vulnerability, and risk
Credit: Dinah Maygarden

So, the question of why one place is more vulnerable to coastal hazards (or other types of hazards) relative to another does not have a simple answer. We must appreciate how the local frequency and intensity of these hazards interact with a diverse set of coastal processes, landforms, infrastructure, and social systems to harm people and things they value.

The question is important to policymakers because if governments and other coastal decision-makers are to make sound decisions to reduce the risk of all members of coastal communities to coastal hazards and prioritize spending to protect their most vulnerable people, places, and property, then they must understand where damage and suffering are likely to be greatest.

Resilience and Adaptive Capacity

The concept of resilience is important for understanding the adaptive capacity dimension of vulnerability to coastal hazards. The resilience of a community is its ability to use available resources to recover and grow from adverse situations, just as a resilient person can more easily bounce back from a setback than a less resilient person. Resilient communities can learn from past experiences and use that knowledge when confronting future problems. Systems with high adaptive capacity are therefore resilient and able to make the necessary changes to deal with coastal hazards. Systems with low adaptive capacity are much less resilient and much more vulnerable to coastal hazards. Later in the module, we will explore several examples of how communities with low adaptive capacity and poor resilience have coped with coastal hazards and how they have learned from these terrible experiences and are working to increase levels of resilience.

First, we will dig deeper into Vulnerability.