Definieren Sie das HAND-basierte Werkzeug zur Fluttiefe und Ausdehnung (Arc Hydro)

kat_h

Hallo, <\/P>

ich versuche, ein Überschwemmungsgebiet eines kleinen Bachs in ArcGIS Pro 2.9 mit Arc Hydro zu begrenzen. <\/P>

Ich folge dem im aktuellen Webinar vorgestellten Workflow: Arc Hydro: Überschwemmung und Vorhersage.<\/P>

1. Gefüllte Senken im LiDAR-basierten DEM
2. Fließrichtung und Fließakkumulation
3. Fließdistanz zur Erstellung eines HAND-Rasters 
4. ArcHydro-Werkzeug: Definieren der HAND-basierten Fluttiefe und Ausdehnung<\/P>

Wie bestimmt man den Parameter 'Input Flood Depth'?
Im Webinar wird erwähnt, dass es die vertikale Schwelle ist, aber ich bin unsicher, was das genau bedeutet. Ist es die maximale Tiefe des Bachs?<\/P>

Ich habe nur LiDAR-Daten, das DEM und die Bachlinie\/Raster verfügbar. <\/P>

Jeder Rat zu diesem Werkzeug ist willkommen, danke! <\/P>

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DeanDjokic

When using HAND method for "flooding", the "Input Flood Depth" is the depth above stream centerline that you want to "flood" with. 

What that specific value is, is up to you.  For example, if you use the "max depth of the creek", that is the equivalent of the "bankfull" and most of the resulting flood polygon should be contained within the channel.  Anything higher should start spilling into the overbanks and you should get "flooding".

So where do you get that number?  Depends on what you are doing.  It can come from the observations (e.g. high water mark or a stage from a gage) or through flow modeling and rating curve to convert flow to depth.  If you are doing the rating curve approach, make sure that the rating curve is based on the same resolution data you used to derive HAND with (or is adjusted accordingly).

And remember that inherent assumption in HAND flood modeling approach is that your water surface is uniform (constant) and parallel to the bottom of the channel.  For each channel segment.  So if you expect that the depth will change (significantly) as you go downstream, you should partition the overall stream into multiple segments that have uniform (but variable from segment to segment) depth and then use "Define HAND-based Flood Depth and Extent from Table" tool to get the floodplain.  More work but might give you better results.

If you stream segment is short, then first follow the approach you have presented (single reach), see if you like the results, and if not, then use the "table" approach.  Note that you will have to reprocess the input data and partition the streams and get their catchments before you can use the "table" approach.

Hope this helps.