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Ian,
<br>
<br>
You may want to look at some U.S. National Weather Service
approaches with what we call Flash Flood Guidance (FFG):
<br>
<br>
<a class="moz-txt-link-freetext"
href="http://www.weather.gov/oh/hrl/gis/workshop3.html">http://www.weather.gov/oh/hrl/gis/workshop3.html</a>
<br>
<a class="moz-txt-link-freetext"
href="http://www.weather.gov/oh/rfcdev/docs/ffgitreport.pdf">http://www.weather.gov/oh/rfcdev/docs/ffgitreport.pdf</a>
<br>
<br>
<a class="moz-txt-link-freetext"
href="http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1054&context=usdeptcommercepub&sei-redir=1#search=%22Application%20National%20Geographic%20Information%20System%20Database%22">http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1054&context=usdeptcommercepub&sei-redir=1#search=%22Application%20National%20Geographic%20Information%20System%20Database%22</a>
<br>
<br>
<br>
Flash Flood prediction is the most problematic in hydrologic
forecasting because we must make predictions for small uncalibrated
catchments and at spatial rainfall scales where rainfall estimation
can be fairly suspect, even with raingauge-corrected radar
estimates.
<br>
<br>
With FFG we try to estimate the amount of rainfall needed within,
say, a 1-hour period, to bring the streams within an individual
pixel (maybe, 1x1 km<sup class="moz-txt-sup">2</sup> area) to
bankfull conditions. Basically, two things are needed:
<br>
<br>
(1) estimates of the flow (runoff) needed to get to bankfull at each
pixel
<br>
(2) in an operational setting, since basin conditions change (wetter
or dryer, for instance) calculating, through a modeling process, the
amount of rainfall needed to achieve (1) — this is the FFG; so, if
that amount of rainfall is either observed or is projected to occur,
a flash flood warning is issued.
<br>
<br>
Doing (2) is not too difficult; the problem is how to find
reasonable estimates of (1) and the references I cited describe some
methods. There is also an approach that tries to identify areas with
high POTENTIAL for flash flooding (<a class="moz-txt-link-freetext"
href="http://www.meted.ucar.edu/hazwarnsys/ffewsrg/FF_EWS.App.D.pdf">http://www.meted.ucar.edu/hazwarnsys/ffewsrg/FF_EWS.App.D.pdf</a>)
due to physical characterisics: slope, soil type, forest density,
percent impervious, landuse, etc. The problem is translating the
potential for flash flooding to flash flood guidance, related to
either observed or predicted rainfall.
<br>
<br>
Regards,
<br>
Tom
<br>
<br>
<br>
On 8/5/11 9:23 AM, Ian Willis wrote:
<blockquote cite="mid:1312550618.2473.2.camel@thorium" type="cite">
<pre wrap="">On Fri, 2011-08-05 at 09:32 +0200, <a class="moz-txt-link-abbreviated" href="mailto:peter.loewe@gmx.de">peter.loewe@gmx.de</a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Hello Ian,
</pre>
<blockquote type="cite">
<pre wrap="">To learn how to use grass I've been trying to solve a real world
problem. The problem that I chose was the flash flooding which occurred
in south eastern Queensland. I'd like to see if grass could have
provided reasonably accurate predictions and see if it could be used as
a warning system.
Ideally what I'd like to do is use the archived radar rainfall
information from <a class="moz-txt-link-freetext" href="http://www.bom.gov.au/products/IDR503.loop.shtml#skip">http://www.bom.gov.au/products/IDR503.loop.shtml#skip</a>
which can be found on <a class="moz-txt-link-freetext" href="http://gw.barratt.com.au/radar/IDR503/2011/01/10/">http://gw.barratt.com.au/radar/IDR503/2011/01/10/</a>
I am intending extrapolate the rainfall rate using the Z value
conversions recommended for east coast lows as per
<a class="moz-txt-link-freetext" href="http://www.catchment.crc.org.au/pdfs/technical200207.pdf">http://www.catchment.crc.org.au/pdfs/technical200207.pdf</a>
and then convert the rainfall rate rasters to the resolution of the
aster dem.
</pre>
</blockquote>
<pre wrap="">...
</pre>
<blockquote type="cite">
<pre wrap="">Any thoughts would be appreciated.
</pre>
</blockquote>
<pre wrap="">
some earlier weather-radar related work with GRASS can be found here:
<a class="moz-txt-link-freetext" href="http://gisws.media.osaka-cu.ac.jp/grass04/viewpaper.php?id=44">http://gisws.media.osaka-cu.ac.jp/grass04/viewpaper.php?id=44</a>
<a class="moz-txt-link-freetext" href="http://onlinelibrary.wiley.com/doi/10.1111/j.1467-9671.2004.00178.x/abstract">http://onlinelibrary.wiley.com/doi/10.1111/j.1467-9671.2004.00178.x/abstract</a>
<a class="moz-txt-link-freetext" href="http://opus.bibliothek.uni-wuerzburg.de/frontdoor.php?source_opus=759&la=en">http://opus.bibliothek.uni-wuerzburg.de/frontdoor.php?source_opus=759&la=en</a> [-> the document is in german, but the technical appendices might be of interest for you -> Z/R realtionship, etc.]
FWIW here's study concerning visual quality assessment for 3D radar-met data:
<a class="moz-txt-link-freetext" href="http://www.docstoc.com/docs/69767645/4D-data-visualisation-and-quality-control">http://www.docstoc.com/docs/69767645/4D-data-visualisation-and-quality-control</a>
Best,
Peter
</pre>
</blockquote>
<pre wrap="">Thanks for the info, I failed german when I was 13 but it might be
interesting to see what a little motivation can do. :-)
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</pre>
</blockquote>
<br>
<br>
<pre class="moz-signature" cols="72">--
Thomas E Adams
National Weather Service
Ohio River Forecast Center
1901 South State Route 134
Wilmington, OH 45177
EMAIL: <a class="moz-txt-link-abbreviated" href="mailto:thomas.adams@noaa.gov">thomas.adams@noaa.gov</a>
VOICE: 937-383-0528
FAX: 937-383-0033</pre>
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