Definujte nástroj HAND-based Flood Depth and Extent (Arc Hydro)

kat_h

Dobrý den, <\/P>

pokusím se vymezit záplavovou oblast malého potoka v ArcGIS Pro 2.9 s Arc Hydro. <\/P>

Postupuji podle pracovního postupu představeného v nedávném webináři: Arc Hydro: Flooding and Forecasting.<\/P>

1. Vyplnění prohlubní v DEM založeném na LiDARu
2. Směr toku a akumulace toku
3. Vzdálenost toku pro vytvoření HAND rastrové vrstvy 
4. Nástroj ArcHydro: Definujte HAND-based Flood Depth and Extent<\/P>

Jak určíte, jaký by měl být parametr 'Input Flood Depth'?
Webinář uvádí, že je to vertikální práh, ale nejsem si jistý, co to znamená. Je to maximální hloubka potoka?<\/P>

Mám k dispozici pouze data LiDAR, DEM a linii/raster potoka. <\/P>

Každá rada ohledně tohoto nástroje je vítána, děkuji! <\/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.