Elevation-Derived Hydrography READ Rules: Connector: Culvert

By NGP Standards and Specifications

Subsurface water conveyances under a transportation feature (Figure 45 and Figure 46).

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A split image showing two different examples of culverts. — **Figure 45.** Examples of culverts, which can be many shapes and sizes and found in a variety of locations. Example A is a very large box culvert running underneath an interstate. Example B shows a much smaller culvert running under a two-lane residential road. (Photo credit: Christy-Ann Archuleta).

Imagery and map showing an example of a culvert. — **Figure 46.** Highway 211 in Virginia crosses unnamed streams with culvert hydrographic features. Source data from the NHD (U.S. Geological Survey, 2020), provides examples of hydrographic feature types but may not have the same density and other characteristics of elevation-derived hydrography.

Delineation

The limit of culvert is the edges of the water conveyance structure.

Representation Rules

Delineate features as points, lines, or polygons based on their area or length along different axes (Table 23).

**Table 23.** Culvert Representation Rules.
Kind of feature object	Area	Shortest Axis	Longest Axis
0-dimensional (point)	--	--	--
1-dimensional (line)	--	greater than 0	greater than 5 feet (1.5 meters)
2-dimensional (polygon)	--	--	--

Special Conditions

Culvert water conveyances may take many forms, for example, a corrugated metal pipe running under a driveway, a massive concrete box under a superhighway, or a platform suspended over flowing water. The purpose of the Connector: Culvert feature in the stream network is to connect the water flowing through a conveyance to the water flowing downstream, without breaking the downstream flow in the network. Connector: Culvert features shall be delineated as (1D) lines connecting the upstream and downstream segments of single-line streams or Artificial path features.

Data Extraction

Capture Conditions

If the culvert is greater than 5 feet (1.5 meters) along the longest axis,

then capture.

Attribute Information

FClass 1— Hydrography feature defined within the collection criteria of the elevation-derived hydrography specifications.
FCode 33401— Connector: Culvert (Subsurface water conveyances under a transportation feature).
EClass 3— Linear feature used for breaching.

Special Conditions

Connector: Culvert feature type shall only be used when the feature is underneath a transportation feature. Other hydrographic feature running under other hydrographic features shall use the Connector (33400) feature type.

Source Interpretation Guidelines

If a structure cannot be definitive identified as a bridge or culvert on the bare earth elevation surface, the feature shall be regarded as a culvert.
Culvert features shall cross transportation features. If a transportation dataset is used to help determine the location of transportation features, it shall be at least as dense as The National Map Transportation Theme layer. If a road is detectable on the elevation surface but not found in the transportation dataset, a Culvert feature must still be placed.