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Flooding is the most common

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and most costly natural disaster in the country.

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In the last two years, more than 8.5 billion in damages

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more than 130 lives lost

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How many are there of you?    -  There's about 40 

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In the bus?

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The question, is what can we do to mitigate this destruction?

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a FIRM, as they call it, a Flood Insurance Rate Map

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is a panel which depicts flood zones

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and these flood zones give an idea of specific risk.

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How likely you may or may not be to encounter a flooding event within a given period of time

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These maps need to be updated because the factors upon which

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the engineering is based change over time. 

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You have changes in the composition of the ground material,

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you may have an increase in the impervious area. You may have better flood study methods available.

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One of the ways to keep

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these FEMA maps up to date is by tracking urban change

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using satellite imagery. Take this suburb of Atlanta, Georgia

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If we look at Landsat images spanning a 27 year period

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we can pinpoint areas of the earth's surface that have changed.

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usually because of construction. Like here,

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where the Mall of Georgia was built.

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A product called NUCI help to mine these images.

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Well, NUCI is especially important when considering risk,

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because it allows us to identify trends in urbanization.

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Now if you identify areas where urban change is accelerating, there are consequences.

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That increase in impervious area are going to mean altered flood characteristics

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likely, and increased risk, because people are probably building houses there.

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Impervious area essentially means ground cover which has been changed

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from the natural state to, say, a paved area, which is going to be concrete or asphalt.

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The infiltration characteristics of that ground material

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have been altered significantly, such that the ground is no longer able to hold water

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which means that local flooding sources are going to receive more water

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and the flooding characteristics are going to change.

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Tracking urban change from space helps everyday people

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understand their flood risk, and take action

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You can't see them, or hear them, but since 1972

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Landsat satellites have been sending us data

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and today, that data helps us manage the high cost of flooding here on earth.

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