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NHD Event Data Dictionary


The data structure of events in the Reach Address Database are patterned upon the event table format defined by the USGS NHD 2.1 schema Exit EPA Disclaimer. Several tools now exist to create hydrologic events using the NHD standard. The following data dictionary is provided as an aid in understanding this format. Note that the Cycle_Year, Start_Date and End_Date fields are not currently part of the USGS NHD 2.1 event model but are vital in the submission of event data to the RAD.

NHD Event Data Model

NHD Point Event

Field Name Data Type NULL? Description
Permanent_Identifier String 40 N 40-char GUID value that uniquely identifies the occurrence of each event.
EventDate Date Y Date an event was created.
ReachCode String 14 Y Reach Code on which the event is located.
ReachSMDate Date Y Reach Version Date.
ReachResolution Long Integer Y Source resolution. See NHD Resolution Domain Table for the list of possible values.
Feature_Permanent_Identifier String 40 Y Permanent_Identifier of NHD feature that is referenced as an event.
FeatureClassRef Long Integer Y NHD feature class that holds FeatureComID. See NHD Feature Class Reference Domain Table for the list of possible values.
Source_Originator String 130 N Originator of the event.
Source_DataDesc String 100 Y Description of the entity.
Source_FeatureID String 40 N Identifier of the entity used in the source data.
FeatureDetailURL String 255 Y URL where detailed event entity data can be found.
Measure Double Y Point measure that the event occurs at upon the reached flowline.
EventType Long Integer N Value indicating the program for which the event has been created. See RAD Programs for values of each program.
EventOffset Double Y Event display offset.
Cycle_Year String 4 Y The cycle year of the event data being submitted. Not all programs have the cycle year concept. For those programs with a cycle year concept this field is mandatory.
Start_Date Date N The start date indicates the date on which the event becomes valid for the program. All program events must have a start date. For programs tracking this value only via year, use April 1st for month and day.
End_Date Date Y The end date indicates the date on which the event is no longer valid or is superceded by new event data in a new record. For event submitters, this field will only be used when submitting historical data to be place directly into the RAD archive tables. Note that the majority of submissions will not utilize this field.
Shape Geometry N Acceptable geometry data types include MDSYS.SDO_GEOMETRY, SDE.ST_GEOMETRY, BLOB of Geographic Markup Language (GML) 2.1, BLOB of Well-Known-Text (WKT) or Well-Known-Text binary format (WKB). Submissions using shapefiles or file geodatabases do not need to add this field. All geometries should utilize the federal standard NAD83 coordinate system or supply specific documentation on projection and datum used.
Objectid Long Integer N Vendor-required unique numeric key.

NHD Line Event

Field Name Data Type NULL? Description
Permanent_Identifier String 40 N 40-char GUID value that uniquely identifies the occurrence of each event.
EventDate Date Y Date an event was created.
ReachCode String 14 Y Reach Code on which the event is located.
ReachSMDate Date Y Reach Version Date.
ReachResolution Long Integer Y Source resolution. See NHD Resolution Domain Table for the list of possible values.
Feature_Permanent_Identifier String 40 Y Permanent_Identifier of NHD feature that is referenced as an event.
FeatureClassRef Long Integer Y NHD feature class that holds FeatureComID. See A href="#Classreference">NHD Feature Class Reference Domain Table for the list of possible values.
Source_Originator String 130 N Originator of the event.
Source_DataDesc String 100 Y Description of the entity.
Source_FeatureID String 40 N Identifier of the entity used in the source data.
FeatureDetailURL String 255 Y URL where detailed event entity data can be found.
FMeasure Double Y Linear Reference starting measure of the NHD reach containing the event.
TMeasure Double Y Linear Reference ending measure of the NHD reach containing the event.
EventOffset Double Y Event display offset.
EventType Long Integer N Value indicating the program for which the event has been created. See RAD Programs for values of each program.
Cycle_Year String 4 Y The cycle year of the event data being submitted. Not all programs have the cycle year concept. For those programs with a cycle year concept this field is mandatory.
Start_Date Date N The start date indicates the date on which the event becomes valid for the program. All program events must have a start date. For programs tracking this value only via year, use April 1st for month and day.
End_Date Date Y The end date indicates the date on which the event is no longer valid or is superceded by new event data in a new record. For event submitters, this field will only be used when submitting historical data to be place directly into the RAD archive tables. Note that the majority of submissions will not utilize this field.
Shape Geometry Y Acceptable geometry data types include MDSYS.SDO_GEOMETRY, SDE.ST_GEOMETRY, BLOB of Geographic Markup Language (GML) 2.1, BLOB of Well-Known-Text (WKT) or Well-Known-Text binary format (WKB). Submissions using shapefiles or file geodatabases do not need to add this field. All geometries should utilize the federal standard NAD83 coordinate system or supply specific documentation on projection and datum used.
ObjectID Long Integer N Vendor-required unique numeric key.

NHD Area Event

Field Name Data Type NULL? Description
Permanent_Identifier String 40 N 40-char GUID value that uniquely identifies the occurrence of each event.
EventDate Date Y Date an event was created.
ReachCode String 14 Y Reach Code on which the event is located.
ReachSMDate Date Y Reach Version Date.
ReachResolution Long Integer Y Source resolution. See NHD Resolution Domain Table for the list of possible values.
Feature_Permanent_Identifier String 40 Y Permanent_Identifier of NHD feature that is referenced as an event.
FeatureClassRef Long Integer Y NHD feature class that holds FeatureComID. See NHD Feature Class Reference Domain Table for the list of possible values.
Source_Originator String 130 N Originator of the event.
Source_DataDesc String 100 Y Description of the entity.
Source_FeatureID String 40 N Identifier of the entity used in the source data.
FeatureDetailURL String 255 Y URL where detailed event entity data can be found.
EventType Long Integer N Value indicating the program for which the event has been created. See RAD Programs for values of each program.
Cycle_Year String 4 Y The cycle year of the event data being submitted. Not all programs have the cycle year concept. For those programs with a cycle year concept this field is mandatory.
Start_Date Date N The start date indicates the date on which the event becomes valid for the program. All program events must have a start date. For programs tracking this value only via year, use April 1st for month and day.
End_Date Date Y The end date indicates the date on which the event is no longer valid or is superceded by new event data in a new record. For event submitters, this field will only be used when submitting historical data to be place directly into the RAD archive tables. Note that the majority of submissions will not utilize this field.
Shape Geometry N Acceptable geometry data types include MDSYS.SDO_GEOMETRY, SDE.ST_GEOMETRY, BLOB of Geographic Markup Language (GML) 2.1, BLOB of Well-Known-Text (WKT) or Well-Known-Text binary format (WKB). Submissions using shapefiles or file geodatabases do not need to add this field. All geometries should utilize the federal standard NAD83 coordinate system or supply specific documentation on projection and datum used.
ObjectID Long Integer N Vendor-required unique numeric key.

NHD Feature to Metadata

Field Name Data Type NULL? Description
Permanent_Identifier String 40 N 40-char GUID value that uniquely identifies the occurrence of each event.
Meta_ProcessID String 40 N 40-char GUID value that uniquely identifies a metadata process description.
ObjectID Long Integer N Vendor-required unique numeric key.

NHD Metadata

Field Name Data Type NULL? Description
Meta_ProcessID String 40 N 40-char GUID value that uniquely identifies a metadata process description.
ProcessDescription String 4000 Y Explanation of the process used to create the data, including parameters or tolerances.
ProcessDate Date Y Date when the data was completed.
AttributeAccuracyReport String 1800 Y Explanation of entities and assignments of values in dataset.
LogicalConsistencyReport String 1000 Y Explanation of fidelity and relationships in dataset, and tests used.
CompletenessReport String 2400 Y Information about omissions, criteria, definitions used to derive dataset.
HorizPositionalAccuracyReport String 3100 Y Horizontal coordinate measurements and description of test used.
VertPositionalAccuracyReport String 3100 Y Vertical coordinate measurements and description of test used.
MetadataStandardName String 100 Y Name of the metadata standard used to document the dataset.
MetadataStandardVersion String 30 Y Identification of the version of the metadata standard used to document it.
MetadataDate Date Y Date the metadata was last created or updated.
DatasetCredit String 4000 Y Recognition of those who contributed to the dataset.
ContactOrganization String 100 Y Name or organization to which type of contact applies.
AddressType String 40 Y Information provided about the address, i.e. mailing, physical, etc.
Address String 100 Y Address line for the address.
City String 40 Y City of the address.
StateOrProvince String 30 Y State or province of the address.
PostalCode String 20 Y ZIP or other postal code of the address.
ContactVoicetelephone String 40 Y Telephone number to reach organization or individual.
ContactInstructions String 120 Y Supplemental instructions to contact organization or individual.
ContactEmailAddress String 40 Y Email address to reach organization or individual.
ObjectID Long Integer N Vendor-required unique numeric key.

NHD Source Citation

Field Name Data Type NULL? Description
Source_DatasetID String 40 N Unique permanent ID value which uniquely identifies a source dataset used.
Title String 255 Y Name by which the dataset is known.
SourceCitationAbbreviation String 255 Y Short form alias for source citation.
Originator String 400 Y Name of organization or individual who developed the dataset.
PublicationDate Date Y Date the dataset is published or made available for release.
BeginningDate Date Y First year of the event (if range of dates applies).
EndingDate Date Y Last year of the event (if range of dates applies).
SourceContribution String 255 Y Brief statement identifying information contributed by source to dataset.
SourceScaleDenominator Long Integer Y Denomination of representative fraction on a map.
TypeOfSourceMedia String 255 Y The medium of the source dataset, i.e. paper, CD-ROM, online, etc.
CalendarDate Date Y The year (if single date applies).
SourceCurrentnessReference String 255 Y The basis on which the source time period of content information of the source data set is determined.
Meta_ProcessID String 40 N 40-char GUID value that uniquely identifies a metadata process description.
ObjectID Long Integer N Vendor-required unique numeric key.

NHD Reach Resolution Domain Table

Value Description
1 Local Resolution
2 High Resolution
3 Medium Resolution

NHD Feature Class Reference Domain Table

Value Description
1 NHDArea
2 NHDFlowline
3 NHDLine
4 NHDPoint
5 NHDWaterbody


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