-------- Original Message --------
Subject:        SILS Bulletin 08-24 Mapping a Flood..Before it Happens
Date:   Wed, 26 Nov 2008 11:02:58 -0700
From:   Sheryle J Jackson <[log in to unmask]>
To:




U.S. Geological Survey
Denver Federal Center, Box 25286
Denver, CO 80225




SILS Information Bulletin

Number: 08-24 Mapping a Flood……..Before it Happens
Date: November 26, 2008

*What's missing from flood forecasts? *

*Maps*—The only maps generally available today are maps used for
planning. They are maps of theoretical floods, not maps of flooding
forecast for an approaching storm. The U.S. Geological Survey (USGS) and
the National Weather Service (NWS) have developed a way to bring flood
forecasting and mapping together, producing flood maps for tomorrow's
flood today. Developed by USGS scientists, the FloodPath software system
can create a flood map days before a storm actually hits and put the map
on the internet in time for those in harm's way to react.

The NWS issues a forecast flood hydrograph (plot of flow vs. time) for a
particular location and USGS uses the hydrograph to create a
flood-inundation map. The USGS has developed methods to make maps of
these forecast floods for long stretches of a river near forecast
points. These maps fill a critical information gap in flood forecasting:
information on when and where floodwater from an approaching storm will
arrive. The maps also show how deep the water is expected to be all
across the floodplain. In essence, these methods combine to make a
somewhat obscure "peak forecast elevation" into a map with flooded
areas, times-of-arrival, and flood depths.

A number of new technologies and methods make the creation of flood
forecast maps possible. First is the ability to get very accurate
elevations throughout the floodplain quickly and affordably. This is
done with "LIDAR" technology (see more below). Second is a computer
program (TRIMR2D) that can simulate flood flows all across the
floodplain and many, many miles downstream from the forecast point.
Third is spatial analysis software (GIS) that turns the model results
into maps and overlays them on other maps like a map of a neighborhood,
or even onto an aerial photograph. Last is software (IMS) that makes the
maps available on the Internet in a flexible and user-friendly way.

More information on this project can be obtained by downloading the USGS
fact sheet at:
*/_ht_/**/_tp://pubs.water.usgs.gov/fs2004-3060_/**/_/_/*; or checking
out the informational page at:
*/_http://wa.water.usgs.gov/projects/pugethazards/urbanhaz/MappingNWS.htm_/*.
For a demonstration of the system go to:
*/_http://wa.water.usgs.gov/cgi/flood_snoqualmie.cgi_/* . For more
information on other USGS products contact the USGS Science Information
and Library Services (SILS) at 1-888-ASK-USGS, or online through the
USGS store at */_http://store.usgs.gov_/**/_._/*


Sheryle Girk-Jackson 303 202 4176, FAX 303 202 4633, email:
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Sheryle J. Girk-Jackson
Technical Information Specialist/Business Acquisitions
USGS/ESIC