HANDベースの洪水深度および範囲ツールの定義（Arc Hydro）

kat_h

こんにちは、 <\/P>

ArcGIS Pro 2.9 と Arc Hydro を使って小さな小川の洪水氾濫原を区画しようとしています。 <\/P>

最近のウェビナー「Arc Hydro: Flooding and Forecasting」で紹介されたワークフローに従っています。<\/P>

1. LiDARベースのDEMでシンクを埋める
2. 流向と流量蓄積
3. HANDラスターを作成するための流距離 
4. ArcHydroツール：HANDベースの洪水深度および範囲を定義<\/P>

「Input Flood Depth」パラメータはどのように決定すればよいですか？
ウェビナーでは垂直しきい値と説明されていますが、それが何を意味するのかよくわかりません。それは小川の最大深さでしょうか？<\/P>

私が持っているのはLiDARデータ、DEM、および小川のライン／ラスターだけです。 <\/P>

このツールについて何かアドバイスがあれば感謝します、ありがとうございます！ <\/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.