Elevation-Derived Hydrography READ Rules: Stream/River

Attribute/Attribute Value

Each feature requires domain codes to be entered into the attribute table for the feature class (Elevation-Derived Hydrography Feature type description, associated geometry, and use classification table in the Elevation-Derived Hydrography Data Acquisition Specifications 2023 revision A2). See “Field Definitions and Domain Values for Attributes” section for more information on Elevation-Derived Hydrography code definitions.

Delineation

The delineation of stream/river features should adhere to the following rules, describing the boundary limits of the feature, and other delineation rules:

• The boundary limit of stream/river:
  • is determined by the position of the visible edge of the banks as depicted on the digital elevation model (as of date of lidar collection).
  • where it enters or leaves lake/pond
    • is determined by the conformation of the land.
  • where it enters sea/ocean
    • is determined by the location where the conformation of the land and water makes the division obvious, or, if the land and water do not suggest an obvious limit, the limit is where the stream reaches a width of 1 nautical mile (6,076.1 feet or 1.15 statute miles) with no further constrictions.
  • Where flattening is required,
    • flattened streams and rivers shall present a flat and level water surface bank-to-bank (perpendicular to the apparent flow centerline).
    • flattened streams and rivers shall present a gradient downhill water surface, following the immediately surrounding terrain.
• Other delineation rules
  • The upper limit of stream/river is where the feature first becomes evident as a channel.
  • In cases of sharp turns of rapidly moving water, where the natural water surface is notably not level bank-to-bank, the water surface will be represented as it exists while maintaining an aesthetic carto- graphic appearance.
  • The entire water surface edge shall be at or below the immediately surrounding terrain.
  • Stream channels shall break at culvert locations leaving the roadway over the culvert intact.
  • Streams shall be continuous at bridge locations.

Representation Rules

When delineating a feature, it must be created with the appropriate geometry, either point, line, or polygon, which is determined by the size of the feature or the length along different axes of the feature (table 16).

Special conditions:

To accommodate variations in the shortest axis of stream/river:

• For lidar base specification collection (not collecting optional features), streams and rivers of approximately 100 feet (30 meters) or greater nominal width shall be flattened (captured as a polygon). The breaklines used for hydroflattening streams and rivers may be used as stream/river polygon features in elevation-derived hydrography.
• For Elevation-Derived Hydrography feature collection, if shortest axis of stream/river is less than 50 feet (15 meters) but greater than or equal to 20 feet (6 meters) for a distance less than 0.6 mile (1 kilometer), and is connected at both ends to a 2-dimensional (polygon) stream/river,

then stream/river is represented as a 2-dimensional (polygon) basic feature object.

• less than 50 feet (15 meters) but greater than or equal to 20 feet (6 meters) for a distance greater than or equal to 0.6 mile (1 kilometer), or less than 20 feet (6 meters) regardless of distance and is connected at both ends to a 2-dimensional (polygon) stream/river,

then stream/river is represented as a 1-dimensional (line) basic feature object.

• greater than or equal to 50 feet (15 meters) but less than 80 feet (24 meters) for a distance less than 0.6 mile (1 kilometer), and is connected at both ends to a 1-dimensional (line) stream/river,

then stream/river is represented as a 1-dimensional (line) basic feature object.

• greater than or equal to 50 feet (15 meters) but less than 80 feet (24 meters) for a distance greater than or equal to 0.6 mile (1 kilometer), or greater than or equal to 80 feet (24 meters) regardless of distance, and is connected at both ends to a 1-dimensional (line) stream/river,

then stream/river is represented as a 2-dimensional (polygon) basic feature object.

Table 16. Stream/River Representation Rules.

Data Extraction

Capture Conditions

If stream/river flows from lake/pond or spring/seep,

then capture.

Attribute Information

FClass 1—Hydrography feature defined within the collection criteria of the elevation-derived hydrography specifications.

FCode 46000—Stream/river (a body of flowing water).

EClass 2—Linear hydrographic features that follow the elevation surface.

OR

FClass 1—Hydrography feature defined within the collection criteria of the elevation-derived hydrography specifications.

FCode 46000—Stream/river (a body of flowing water).

EClass 11— Polygon created from breakline—Polygon derived from the breaklines used for hydroflattening the elevation surface (3D polygon).

OR

FClass 1—Hydrography feature defined within the collection criteria of the elevation-derived hydrography specifications.

FCode 46000—Stream/river (a body of flowing water).

EClass 12— Polygon created from hydroflattened surface—Polygon corresponding to a hydroflattened surface, but breakline is either not available or not horizontally or vertically aligned appropriately with the DEM surface. For use in Alaska or where breaklines do not meet cartographic or horizontal requirements.

OR

FClass 1—Hydrography feature defined within the collection criteria of the elevation-derived hydrography specifications.

FCode 46000—Stream/river (a body of flowing water).

EClass 13— Polygon created without using elevation breakline and the surface of the waterbody is not hydroflattened in the source DEM.

Source Interpretation Guidelines

The minimum size for islands within stream/river is 0.12 acres (approximately 500 square meters).

For lidar base specification hydrographic breakline, permanent islands 1 acre (4,000 square meters) or larger shall be delineated within all waterbodies.