NHDPointEventFC

Point events are tied to a specific location on a stream network by a reachcode and a measure. While several types of Point Events are accepted back into the National Database, additional Point Event Types may be used on an individual basis.

A Water Quality Monitoring Station is an example of a Point Event.

 

The attributes associated with NHDLineEventFC are as follows:

Field Name

Definition

Comments

Permanent_Identifier

Global ID and GUID data types store registry style strings consisting of 36 characters enclosed in curly brackets. These strings uniquely identify a feature or table row within a geodatabase and across geodatabases. This is how features are tracked in one-way and two-way geodatabase replication.

 

EventDate

Date an event was created or modified.

 

ReachCode

Reach Code on which the event is located.

 

ReachSMDate

Reach Spatial Modification Date.

The version date tracks the last time that the reach represented by ReachCode experienced a change in geometry.  When the ReachSMDate in the event record and the ReachSMDate in the NHDReachCode_ComID table disagree, the position of the event along the network may need to be updated.

ReachResolution

Source resolution.  Currently NHD is available as separate resolutions.  Plans are to develop a single-resolution database holding the highest resolution data with tools to allow for generalization

Domain of values:

Local >1:12,000

High 1:24,000/12,000

Medium 1:100,000

Feature_Permanent_Identifier

Permanent_Identifier of NHD feature that the event is referenced to.

 

FeatureClassRef

NHD feature class that holds FeatureComID

 

SourceOriginator

Originator of the event

 

SourceDataDesc

Description of the entity

 

SourceFeatID

Identifier of the entity used in the  source data.

 

FeatureDetailURL

URL where detailed event entity data can be found

 

Measure

Measure along the reach, in percent from downstream end, where a point event is located.

 

EventOffset

Distance from the network to be used to display event

Negative offsets display the event to the left of the network and positive offsets display the event to the right of the line.   Offsets are useful for displaying overlapping events.

 

EventType

Type of entity in an event