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http://opengeospatial.github.io/HY_Features/
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Reach Catchment concept. #203

Closed dblodgett-usgs closed 7 years ago

dblodgett-usgs commented 7 years ago

Give a nod to the concept of a “reach-catchment” when introducing the correspondence between catchment and flowpath.

Reach and reach catchment. As the term reach is not used, neither is reach catchment. The concepts though are discussed and illustrated in figures. Nevertheless, some crucial ideas are missing. A reach is a constrained notion of a flowpath, every instance of these flowpaths has a corresponding catchment, and these catchments form a true coverage. This is worth stating, but to do so requires that an elementary flowpath equivalent to a reach be defined. Additionally, if a hydrographic network is simplified by removing shorter first-order streams (or smaller first-order catchments or some other related measure) iteratively to the desired level of generalization, then the corresponding catchments become aggregations of the original catchments. Arguably this is an important property when trying to relate representations at different scales. The notion of a reach catchment is fundamental to the NHD and will likely be in a future version of Canada’s NHN. Some hydrology packages require reach catchments. So it would be very germane for HY_Features to recognize the concept in some fashion. Please also see related comments found a couple of pages below on directed graph and topology.

Reach catchments are of fundamental importance, both conceptually and literally as a basic unit of aggregation. They are required by some widely used hydrologic software packages such as SPARROW. It is recommended that reaches and reach catchments be recognized in HY_Features, although other terms could be used. For example, an elementary flowpath could be specified as a flowpath constrained such that its interior (the line minus its endpoints) cannot include confluences. An e lementary catchment has a one-to-one relationship with an elementary flowpath. Aggregation is relevant to both.

dblodgett-usgs commented 7 years ago

The group agreed to this at the Delft TC. Fixes an issue in #182

dblodgett-usgs commented 7 years ago

Response to review: A section regarding the "scheme" of an implemented dataset with regard to HY_Features will be added. The "reach-catchment" arrangement described here is clearly a "scheme" that is supported by HY_Features and will be used to illustrate the "scheme" concept.

dblodgett-usgs commented 7 years ago

Added a paragraph to the new scheme section addressing this.

dblodgett-usgs commented 7 years ago

Noting in this issue that the new section 6.2.1 could use review. Other issues addressed by 6.2.1 are: #194, #202, #203, #205.