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National Hydrography Dataset

"Include Flow" Option

Availability

The "Include Flow" option works when subbasins are selected as reference polygons. Turning on this option considerably increases the time to complete an extract job.

Flow Table

In the NHD Model, the NHDFlow table provides feature to feature flow information for the NHDFlowline feature class. This flow table data is redundant with the network flow navigation available in the geometric network in both the personal and file geodatabase downloads. The flow table is intended to support interoperability with applications outside of ESRI geodatabase solutions. The records of this table contain ComIDs, the NHDFlowline primary feature identifier, in two fields (FromComID, ToComID) which provide the feature to feature flow relationship.  In the sample records provided below, the table indicates that the feature 23988224 flows into feature 23988222. The sample records also indicate that feature 23988222 then flows into 23988220. A record either flowing from a FromComID of zero or to a ToComID of zero indicates that the other feature in the record is a headwater or “end-of-drain” respectively.  In the sample records, record 97 shows that 23988250 is a headwater feature.

 

NHDFlow

OBJECTID

FromComID

ToComID

DeltaLevel

Direction

ToComIDMeas

91

23988224

23988222

0

709

0

92

23988258

23988256

0

709

0

93

23988346

23988256

0

709

0

94

23988318

23988220

0

709

0

95

23988222

23988220

0

709

0

96

23988188

23990861

0

709

0

97

0

23988250

0

712

0

 

 

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