Storm That Drowned a City
will watch a teacher demonstration modeling how wetlands can help reduce a
hurricane's impact and describe what the model represents.
Students will be able to:
record data related to how different meshed materials affect a steam
compare results and rate meshed materials according to how much steam
each material blocked.
infer how wetlands can sometimes help protect land from hurricanes.
- steam kettle with spout
- hot plate or equivalent heat source
- protective gloves, such as oven mitts or rubber gloves
- materials with different mesh size, such as coarse window screening, fine window screening, cheesecloth, facial tissue, paper towel, cotton cloth (e.g., T-shirt), flannel, and diaper
- solid barrier, such as a block of wood, sheet of cardboard, or spatula
- copy of the "Wetlands and Hurricanes" student handout
Hurricanes need two basic ingredients to begin: a source of energy (warm
tropical ocean waters) and a disturbance in the atmosphere (such as a
thunderstorm). Most Atlantic hurricanes start as storm systems off the coast of
West Africa. These storms move westward over warm, tropical ocean waters. A
hurricane forms when warm, moist air rises from the ocean surface and begins to
condense into storm clouds and rain. As the water condenses it releases heat,
which warms the air around it. This warm air begins to rise; as it does so it
is replaced by more warm, moist air from the ocean below. This cycle starts the
hurricane's spinning motion. As a hurricane travels over the warm water it can
gain more energy and increase in strength (a hurricane starts as a tropical
depression before developing into a tropical storm and then a hurricane). A
hurricane's strength diminishes as it moves over land and is robbed of its warm
water energy source. Dense wetlands can help weaken a hurricane by breaking the
connection between the hurricane and warm ocean water. Wetlands can also act as
a physical barrier, slowing and reducing the force of the waves that reach the
Before Hurricane Katrina hit in 2005, the rate of loss of wetlands along
Louisiana's coast had been about 75 square kilometers per year, a loss that had
been occurring for several decades. Some of this was due to natural processes
such as tides and storm surges. Other losses resulted from dredging canals for
sources of oil and the use of heavy commercial and recreational boat traffic
through the wetlands. In addition, the construction of levees and concrete
channels to control the Mississippi River starved the coastal marshes of the
fresh water and sediment necessary to restore and preserve them.
As a general rule, about a kilometer and a half of marsh can reduce a coastal
storm surge by about 30 centimeters. The surge that hit the Gulf Coast when
Katrina hit was close to nine meters—the highest ever recorded. The surge
was about three meters. Some scientists believe that a few kilometers of marsh
could have lessoned Katrina's impact on Louisiana's coast.
In this activity, students examine how wetlands can deprive a hurricane of some
of the warm, moist air that supplies its energy. The steam represents the
hurricane and different types of meshed materials represent dense and sparse
wetlands. Students will record what happens to the plume of steam (hurricane)
when different materials are placed in its path.
hurricane: Intense rotating oceanic weather system with winds of at
least 119 kilometers an hour.
wetlands: Lands that saturate with water. Wetlands vary greatly, and are
found on every continent except Antarctica.
Have students locate the tropical zone south of the equator on a map (the
regions between 5° and 20° north and south of the equator are the
belts where hurricanes can form). Review with students how hurricanes
Choose the materials you would like to use. Make sure you use at least three
materials of different mesh densities (see Activity Answer on page 5 for sample
results.) Organize students into teams. Distribute copies of the "Wetlands and
Hurricanes" handout to each student.
Boil the water in the kettle. (You can make the steam more apparent by
placing the kettle against a dark background.) Safety note: Steam
scalds! Wear protective gloves. When placing materials over the spout tip of
the kettle, as instructed below, hold the materials so your hands are below the
spout tip. Stretch the materials taut over the spout's opening so steam goes
through the materials instead of being channeled out to the sides where it can
scald your hands.
As the water heats, tell students that the water in the kettle represents
the ocean, the hot plate represents the heat from Earth's tropical zone that
warms ocean water, and the steam plume represents a hurricane.
Ask students to record their observations about the plume of steam.
Ask students to predict how the different materials will affect the plume
when you place them in its path. Have them record their predictions and
Put on the protective gloves and place one of the materials across the tip
of the spout. Have the class observe and record the effects on the plume of
steam. Repeat the demonstration using the remaining materials. Explore how
students' predictions compare to what actually happened.
Have each student answer the questions on his or her handout. Work with
students to find answers to any additional questions they may have about
As an extension, have students research where the nearest wetland area is to
their school. Consider with students different types of wetlands such as
swamps, marshes, and bogs, and have students find on a local map the wetlands
(and their size) that are closest to their school. Have them estimate the size
of the wetlands and find during which months the wetlands are most likely
saturated with water. Ask students to research the dominant soil type(s) and
the names of some of the plants and animals that inhabit the wetland.
as wetlands interfere with a hurricane's supply of warm, moist air, the
materials placed over the kettle spout disrupt the connection between the warm,
moist air produced inside the kettle and the plume of steam at the spout. The
class should see that the plume's strength diminishes as the mesh gets
Effect of Different Materials on a Steam Plume
Effect on the Steam Plume
change in plume's shape or speed at which steam comes out of spout
change in plume's shape or speed at which steam comes out of spout
of steam coming out of spout slows slightly
tissue/Paper towel/ Cotton cloth (T-shirt)
of steam coming out of spout slows a little; steam rises straight up rather
than leaving the spout forcefully at an angle
of steam coming out of spout slows considerably; steam cloud becomes just a
series of wisps
cloud significantly disrupted
Student Handout Questions
What kind of wetlands do the coarse-meshed materials represent? The
course-meshed materials represent sparse wetlands.
What kind of wetlands do the fine-meshed materials represent? The
fine-meshed materials represent dense wetlands.
Why did the fine-meshed materials weaken the steam plume? The fine
material reduced the supply of warm, moist air from inside the kettle.
How do healthy wetlands help protect a coastal area from hurricanes?
Dense wetlands reduce the amount of warm, moist air going into a
Hurricanes die out when they travel inland because, when over land, they are
no longer supplied with the warm, energy-rich, moist ocean air. In this kettle
hurricane model, what could you do to the model to represent what happens when
a hurricane travels inland? Students' suggestions may include interrupting
the flow of steam with a solid barrier, such as cardboard, or turning off the
hot plate to eliminate the supply of warm, moist air.
What are this model's strengths in representing hurricanes and the effect of
wetlands? The model accurately shows one way in which wetlands can reduce
the impact of a hurricane.
What are this model's limitations? The model shows neither the complexity
of a hurricane system nor the true nature of a wetland area.
NOVA—Storm That Drowned a City
Read an interview with one scientist who predicted the effects of a
Katrina-like hurricane, learn about New Orleans' 300-year battle with water,
track the hurricane's progression, zoom in on key sites that played a role in
the Big Easy's flooding, and map the effect Katrina would have had on your
Provides a set of classroom activities related to estuaries.
Describes where and how hurricanes form, the damage they can cause, and how
they are rated in intensity.
National Wetlands Inventory
Provides information on the characteristics, extent, and status of the nation's
What Is a Hurricane?
Provides general facts about hurricanes and links to tracking maps, forecasting
information, and dates for Category 4 and Category 5 hurricanes that have
occurred this century.
by William Niering. Alfred A. Knopf, 1985.
Includes descriptions of different kinds of wetlands and the plants and animals
The "Wetlands and Hurricanes" activity aligns with the following National
Science Education Standards (see books.nap.edu/html/nses).
Science Standard D
Earth and Space Science
Structure of the Earth system
Science Standard F
Science in Personal and Social Perspectives
Classroom Activity Author
Developed by WGBH Educational Outreach staff.