Name__________________________________________ #________ Date________________ Hour______
Center #3: Considering Flood Risk
Directions: Use the laminated Considering Flood Risk activity sheet, the laminated Map of Boulder, Colorado, and
the Background Information on Floodplains to complete this activity.
Part I Background Information on Floodplains Directions: Read the passage before attempting to complete the
activity.
Risk is defined as a combination of the probability of an event occurring and the consequences if it does occur. For
example, the probability of a flood occurring in a low-lying area next to a river might be quite high, but if it is a natural
setting with no negative consequence from a flood aside from the deposition of some sediment, then the risk is low.
If, on the other hand, a town is next to the river, then there would be negative consequences for it and its residents
should a flood occur. Risk would then be high.
The probability of a flood occurring in the 100-year floodplain is one in 100 or 1 percent each year. It does not mean
that a flood happens every 100 years. With a 1-percent probability, floods could happen two years in a row. Likewise,
the 500-year floodplain is the area where the probability of flooding is one in 500 or 0.2 percent each year.
Boulder, Colorado is at the foot of the Rocky Mountains. Several narrow valleys lie to the west of the city. When
rainstorms drop large amounts of water in one of these valleys, it flows downhill into the city. Often thunderstorms in
the area are isolated to a particular region, meaning that flooding could happen in a creek that comes from one
valley where the rainstorm has stalled and not another. However, in September 2013, a very large rainstorm parked
itself over the entire region for several days causing widespread flooding of all the waterways that pass through the
city.
The probability of flooding can also be affected in various areas of the world by differences in topography, rapid
snowmelt, ice jams in rivers, the permeability of the land, and proximity to coasts that are vulnerable to flooding
during storms like hurricanes.
Part II Write Recommendations Directions: Refer to the laminated Considering Flood Risk activity sheet and the
laminated Map of Boulder, Colorado to write recommendations to each potential builder in the spaces provided
below.
1. Jane Higgin’s situation:________________________________________________________________________
____________________________________________________________________________________________
____________________________________________________________________________________________
____________________________________________________________________________________________
____________________________________________________________________________________________
____________________________________________________________________________________________
____________________________________________________________________________________________
2. Max Washington’s situation: ___________________________________________________________________
____________________________________________________________________________________________
____________________________________________________________________________________________
____________________________________________________________________________________________
____________________________________________________________________________________________
____________________________________________________________________________________________
____________________________________________________________________________________________
3. Juan and Marsha Martinez’s situation:____________________________________________________________
____________________________________________________________________________________________
____________________________________________________________________________________________
____________________________________________________________________________________________
____________________________________________________________________________________________
____________________________________________________________________________________________
____________________________________________________________________________________________
4. Boulder Birders’ situation: _____________________________________________________________________
____________________________________________________________________________________________
____________________________________________________________________________________________
____________________________________________________________________________________________
____________________________________________________________________________________________
____________________________________________________________________________________________
____________________________________________________________________________________________
Part III Explaining Mitigation Directions: Answer the following questions about flood mitigation below.
1. What does flood mitigation mean? ______________________________________________________________
____________________________________________________________________________________________
2. What are some flood common mitigation practices in coastal areas, such as Florida and South Carolina?_______
____________________________________________________________________________________________
____________________________________________________________________________________________
3. What is the natural floodplain in our area that tends to close after heavy rains or during the spring thaw? _______
____________________________________________________________________________________________
4. Why does the natural floodplain identified in question #3 close? What causes the flooding after heavy rains or
during the spring thaw?
___________________________________________________________________________________________
____________________________________________________________________________________________
5. Look for the vocabulary card taped to the supply tub for this center’s vocabulary terms.