Eliminando Polígonos de Sub-bacias

Question

<\/HEAD>Eu tenho uma classe de feição que contém polígonos representando bacias derivadas do uso da ferramenta Adjoint Catchment Processing no Arc Hydro Tools. Pelo que sei, essa classe de feição contém polígonos de todas as bacias do meu DEM acima de um certo limite de área de drenagem, incluindo as bacias que estão aninhadas dentro de uma bacia maior (sub-bacias). Eu eliminei todos os polígonos com áreas acima de um limite superior de área, bem como polígonos abaixo de um limite inferior de área, usando "Selecionar por Atributos" na tabela de atributos da classe de feição e excluindo as feições selecionadas, mas ainda restam polígonos que são sobrepostos por polígonos maiores (essencialmente as sub-bacias dentro de uma bacia maior). Eu gostaria de eliminar todos os polígonos que são sub-bacias e contêm áreas que estão contidas dentro de um polígono maior na mesma classe de feição, mas todas as ferramentas que tentei até agora não produzem o resultado desejado. Qualquer ajuda seria muito apreciada. Arc Hydro<\/A><\/P><\/BODY><\/HTML>

MarkBoucher · Answer

Brian, In response to:

"To the best of my knowledge, this feature class [AdjointCatchment] contains polygons of all of the catchments from my DEM above a certain threshold drainage area, including the catchments that are nested within a larger catchment (subcatchments)."

Lets say you wanted to delineate a watershed that did not coincide with a DrainagePoint. Delineating only using the flow direction grid (fdr) is very slow. If we calculate the Catchments at the DrainagePoints, some of that work is already done.

The AdjointCatchment (ACat for short) is precisely created to overlap the Catchment polygons and allow us to capitalize on the Catchment polys by conglomerating (adjoining) them. Then to delineate any point, one must only delineate a small portion downstream of a DrainagePoint using the fdr grid and then use the ACat polys to immediately define the rest of the delineation.

MarkBoucher · Answer

The appropriate way to use our Arc Hydro is to develop the Catchments and AdjointCatchments first and leave them alone. The Catchments  and AdjointCatchments are used by Arc Hydro in performing the delineation by "Batch_Points".  Their whole purpose is to speed up the delineation process.

You place "Batch_Points" at the locations where you want to calculate flows. You can use the drainage points created by Arc Hydro (Copy or snap to while creating. The Batch_Point feature table has specific fields. Create at least one point using the Batch Point creation tool, then copy other points to that dataset). Then use the Arc Hydro Watershed Processing tool Batch Subwatershed Delineation to delineate the Subwatersheds you want for your study based on the Batch_Points locations. GeoHMS has a tool that "imports" Batch_Points. I use this all the time without having to use other GeoHMS functions.

In Arc Hydro, Subwatersheds do not overlap and Watersheds do overlap. So, pick which you want. You can create both. They are created in different datasets. To use the batch points again, you have to calculate the BatchDone field to zero.

I'm doing this from home and don't have access to the software to make sure all of my terms are correct. I may look at this tomorrow and double check that I'm communicating correctly. I have updated this reply considerably after getting into the office this AM.

Mark Boucher