# NHDMetadata

ProcessDescription:
Replaced branched and disjoint (disconnected) reaches with linear reaches in NHDFlowline.  This change occurred during the conversion to the geodatabase model.  Each NHDFlowline that was part of a branched or disjoint reach was assigned to a new reach.  The ComID of the NHDFlowline was unchanged   The change information from the old reach to the new reach was captured in the NHDReachCrossReference table.  Each new reach has M values assigned from 0 to 100.


ProcessDescription:
Merged and/or split area features (NHDWaterbody, NHDArea, region.wb, region.lm) and updated associated artificial path WBAreaComID (wb_com_id) values.  This change occurred during the conversion to the geodatabase model.  If adjacent or overlapping area features had identical classifications, including ReachCode where applicable, the features were merged.  If an area feature exceeded 100 sq. km. (25 sq. km. for canal/ditch, stream/river, or submerged stream) and crossed a subbasin boundary, the feature was split at the subbasin boundary.  If any sliver polygons of a size of less than 5 sq. km. adjoined the split features, the slivers were merged back into the larger area feature.  Merged or split area features were assigned a new ComID.


ProcessDescription:
Updated WBAreaComID (WB_COM_ID) on NHDFlowline (route.drain) where the associated area features were assigned new ComIDs from merge or split during the conversion to geodatabase.


ProcessDescription:
Edited NHDFlowline (route.drain) features to improve network connectivity and network flow.  This edit occurred during the conversion to the geodatabase model.  Features we snapped, spatially modified, flipped, added, or deleted to assure network integrity.  Also, some feature classification modifications occurred to convert artificial paths to coastlines.


ProcessDescription:
Create high-resolution NHD from USGS DLG data. DLG files were  converted to ArcInfo coverages and projected to the New  Hampshire State Plane coordinate system (NHSP NAD83 Feet).  Having the data in NHSP allowed for the draping of the vector  data with the State of New Hampshire's projected Digital  Raster Graphic Images (DRGs, source: USGS), when needed for  feature verification/connection. The DLG coverages were  edgematched using a 40 foot snapping tolerance.  Features  outside the tolerance were not moved; instead, a feature of  type connector was added to join the features. DLG feature  coding was visually verified using hardcopy plots. Coverages  were then paneled into one coverage and arcs within 40 feet  of each other along the neatline were again snapped together  if the feature types were the same.  Next, the 11-digit  Hydrologic Unit Code (HUC) boundary was used to extract  features from the paneled coverage that fell within the  boundary. Next, arcs from the extracted coverage were grouped  in order to examine the connectivity of the data set for  flow determination. In some cases it was necessary to correct  digitizing errors.  Using contour lines from the New Hampshire  DRGs, lines called connectors were added to join features that  were deemed to have flow between each other.  All arcs were  directed downstream and the nodes were prepared to help create artificial paths through 2-D waterbodies and complete the flow through the hydrography network.  The artificial path coverage was combined with the single line stream network to create the drainage network.  The drainage network was grouped again,  and each group was directed downstream.  The data was then  appended to conform to the 8-digit HUC boundaries.  Feature codes  (fcodes) were assigned to network and waterbody features through  a crosswalk that converts DLG-3 attributes to fcodes, where an  fcode is a five digit integer that encodes a set of feature type  characteristics.  Reach codes and associated attributes were  conflated from the 100K NHD data to the 24K drainage network and  2-D waterbodies. Several checks were performed to validate the  reach transfer process. Any reach codes that could not be  maintained are tracked in the Reach Cross Reference table. New  reaches that do not exist in the 100K data were defined  according to reach delineation rules  (See http://nhd.usgs.gov/chapter1/index.html).   New waterbody reaches were assigned to 2-D lake/pond and  reservoir features that do not exist in the 100K NHD.  New  reaches were assigned reach code values that are sequentially  ordered to 2-D and then 1-D reaches. New 24K reach codes are  larger than any existing 100K reach code in the associated  Catalog Unit. Additional Geographic Names that exist in the  Geographic Names Information System (GNIS) were added to reaches  in the 24K dataset. Names for the 24K drainage network were  interactively transferred from the vector GNIS coverage.  Additional GNIS names for waterbody features were also added.

AttributeAccuracyreport:
The accuracy of the attributes of the source Digital Line  Graph data is estimated to be 98.5 percent. One or more of  the following methods were used to test attribute accuracy:  manual comparison of the source with hardcopy plots;  symbolized display of the digital line graph on an  interactive computer graphic system; selected attributes  that could not be visually verified on plots or on screen  were interactively queried and verified on screen. In  addition, software validated feature types and  characteristics against a master set of types and  characteristics,checked that combinations of types and  characteristics were valid, and that types and  characteristics were valid for the delineation of the  feature. Feature types, characteristics, and other  attributes conform to the Standards for National  Hydrography Dataset - High Resolution (USGS, 1999) as of  the date they were loaded into the database. All names  on the 1:24,000-scale reaches were validated against a  April 1999 extract from the Geographic Names Information  System. The entry and identifier for the names match those  in the Geographic Names Information System. The association  of each name to reaches has been interactively checked  against the April 1999 Geographic Names Information System  names extract, however, operator error could in some cases  apply a name to a wrong reach.

LogicalConsistencyReport:
Points, nodes, lines, and areas conform to topological rules.   Lines intersect only at nodes, and all nodes anchor the ends  of lines.  Lines do not overshoot or undershoot other lines  where they are supposed to meet. There are no duplicate lines.  Lines bound areas and lines identify the areas to the left and  right of the lines.  Gaps and overlaps among areas do not  exist.  All areas close.

CompletenessReport:
The completeness of the data reflects the published USGS  topographic quadrangle usually, supplemented by Digital  Orthophoto Quadrangles(DOQ's). Features found on the ground may  have been eliminated or generalized on the source map because  of scale and legibility constraints.  In general, streams longer  than one mile (approximately 1.6 kilometers) were collected.  Most streams that flow from a lake were collected regardless  of their length.  Only definite channels were collected so  not all swamp/marsh features have stream/rivers delineated  through them.  Lake/ponds 100 feet or greater in the shortest  axis were collected.  Note, however, that these general rules  were applied unevenly among maps during compilation.  Transport reaches are defined on nearly all features of type  stream/river, canal/ditch, artificial path, and connector.   Waterbody reaches are defined on all lake/pond features. Detailed  capture conditions are provided for every feature type in the  Standards for National Hydrography Dataset - High Resolution  (USGS, 1999), available online through  http://mapping.usgs.gov/standards/.

HorizPositionalAccuracyReport:
Statements of horizontal positional accuracy are based on  accuracy statements made for U.S. Geological Survey topographic  quadrangle maps. These maps were compiled to meet National Map  Accuracy Standards. For horizontal accuracy, this standard is  met if at least 90 percent of points tested are within 0.02  inch (at map scale) of the true position.  Additional offsets  to positions may have been introduced where feature density is  high to improve the legibility of map symbols.In addition, the  digitizing of maps is estimated to contain a horizontal  positional error of less than or equal to 0.003 inch standard  error(at map scale) in the two component directions relative  to the source maps.  Visual comparison between the map graphic  (including digital scans of the graphic) and plots or digital  displays of points, lines, and areas, is used as control to  assess the positional accuracy of digital data. Digital map  elements along the adjoining edges of data sets are aligned if  they are within a 0.02 inch tolerance (at map scale). Features  with like dimensionality (for example, features that all are  delineated with lines), with or without like characteristics,  that are within the tolerance are aligned by moving the  features equally to a common point. Features outside the  tolerance are not moved; instead, a feature of type connector  is added to join the features.

VertPositionalAccuracyReport:
Statements of vertical positional accuracy for elevation of  water surfaces are  based on accuracy statements made for  U.S. Geological Survey topographicquadrangle maps.  These  maps were compiled to meet National Map Accuracy Standards.   For vertical accuracy, this standard is met if at least 90  percent of well-defined points tested are within one-half  contour interval of the correct value.  Elevations of water  surface printed on the published map meet this standard;  the contour intervals of the maps vary. These elevations  were transcribed into the digital data; the accuracy of  this transcription was checked by visual comparison between  the data and the map.

MetadataStandardName:
FGDC Content Standards For Digital Geospatial Metadata

DataSetCredit:
U.S. Geological Survey in cooperation with U. S. Environmental Protection Agency, Complex Systems Research Center at the University of New Hampshire, and New Hampshire Department of Environmental Services.

Address:
Mid-Continent Mapping Center - 1400 Independence Rd


ProcessDescription:
Create high-resolution NHD from USGS DLG data. DLG files were  converted to ArcInfo coverages and projected to the New  Hampshire State Plane coordinate system (NHSP NAD83 Feet).  Having the data in NHSP allowed for the draping of the vector  data with the State of New Hampshire's projected Digital  Raster Graphic Images (DRGs, source: USGS), when needed for  feature verification/connection. The DLG coverages were  edgematched using a 40 foot snapping tolerance.  Features  outside the tolerance were not moved; instead, a feature of  type connector was added to join the features. DLG feature  coding was visually verified using hardcopy plots. Coverages  were then paneled into one coverage and arcs within 40 feet  of each other along the neatline were again snapped together  if the feature types were the same.  Next, the 11-digit  Hydrologic Unit Code (HUC) boundary was used to extract  features from the paneled coverage that fell within the  boundary. Next, arcs from the extracted coverage were grouped  in order to examine the connectivity of the data set for  flow determination. In some cases it was necessary to correct  digitizing errors.  Using contour lines from the New Hampshire  DRGs, lines called connectors were added to join features that  were deemed to have flow between each other.  All arcs were  directed downstream and the nodes were prepared to help create artificial paths through 2-D waterbodies and complete the flow through the hydrography network.  The artificial path coverage was combined with the single line stream network to create the drainage network.  The drainage network was grouped again,  and each group was directed downstream.  The data was then  appended to conform to the 8-digit CU boundaries.  Feature codes  (fcodes)were assigned to network and waterbody features through  a crosswalk that converts DLG-3 attributes to fcodes, where an  fcode is a five digit integer that encodes a set of feature type  characteristics.  Reach codes and associated attributes were  conflated from the 100K NHD data to the 24K drainage network and  2-D waterbodies. Several checks were performed to validate the  reach transfer process. Any reach codes that could not be  maintained are tracked in the Reach Cross Reference table. New  reaches that do not exist in the 100K data were defined  according to reach delineation rules  (See http://nhd.usgs.gov/chapter1/index.html).   New waterbody reaches were assigned to 2-D lake/pond and  reservoir features that do not exist in the 100K NHD.  New  reaches were assigned reach code values that are sequentially  ordered to 2-D and then 1-D reaches. New 24K reach codes are  larger than any existing 100K reach code in the associated  Catalog Unit. Additional Geographic Names that exist in the  Geographic Names Information System (GNIS) were added to reaches  in the 24K dataset. Names for the 24K drainage network were  interactively transferred from the vector GNIS coverage.  Additional GNIS names for waterbody features were also added.

Address:
Mid-Continent Mapping Center - 1400 Independence Road


ProcessDescription:
1:100,000 scale medium-resolution stream gage shapefiles obtained from the U.S. Geological Survey Nation Water Information System and 1:24,000 scale high-resolution watercourse digital data sets collected by the U.S. Geological Survey, National Geospatial Technical Operations Centers (NGTOC), were used to linear reference the medium resolution 0d stream gages to the corresponding high-resolution watercourse geometry.  Quality Assurance was preformed to guarantee that each gage was properly indexed to the watercourse geometry and that the correct spatial address and location on the network were obtained.  The position of the high-resolution gages was not further enhanced based on 1:24,000 scale sources such as DRGs or DOQs.


ProcessDescription:
Create high-resolution NHD Dam features and events from the National Inventory of Dams by snapping NID position to the appropriate position on the appropriate NHDFlowline and obtaining the network address.  Since dams are located on the network, they may be offset from the actual physical position.  Dams that cannot be logically associated with a NHDFlowline are not included.  Dams under a size threshold of 2,400 acre-feet normal storage capacity are generally not included

DataSetCredit:
U.S. Geological Survey, National Geospatial Technical Operations Center

Address:
U.S. Geological Survey, National Technical Operations Center, P.O. Box 25046


ProcessDescription:
Maintenance Lite 1D review. Evaluate and correct network connectivity and flow direction as needed. Review and edit gapped GNIS Name and IDs and branched or gapped ReachCodes. Repair overlapping flowline features.


Address:
U.S. Geological Survey, National Geospatial Technical Operations Center, P.O. Box 25046


ProcessDescription:
Update GNIS ids and names to match the current GNIS ids/names.


ProcessDescription:
Reach codes migrated to match new Watershed Boundary Dataset (WBD) boundaries, which are different from the 250 HUC boundaries used previously to derive reach codes.

DataSetCredit:
U.S. Geological Survey National Geospatial Technical Operations Center (USGS\NGTOC)


ProcessDescription:
NHD High Resolution Maintenance Lite II by Sub Region.  Procedures include the following: Topology is checked for:  NHDWaterbodys must not overlap; NHDWaterbody must not overlap NHDArea; and NHDAreas must not overlap. Check all reaches to ensure that they have MValues (measures). Remove branched GNIS names. Check entire extent of GNIS name for gaps. Check all WBAreaComIDs and correct or add as necessary. Check all coastlines (coincident with 2D features) and correct as necessary. Extract transactional updates (XML) from updated personal geodatabase and load updates into original personal geodatabase for final transaction review. Re-check data integrity based on previous Sub Region Maintenance Lite.

Address:
U.S. Geological Survey, National Geospatial Technical Operations Center, 1400 Independence Road


ProcessDescription:
Maintenance of known errors to the NHD using 1 foot ortho imagery from the NHDOT taken in 2006.  Changes include correction of flow directions, changes of attributes from connector to stream/river, and addition of flowlines from other sources.


ProcessDescription:
Maintenance of known errors to the NHD using 1 foot ortho-photography from NHDOT


# NHDSourceCitation

Originator:
U.S. Geological Survey in cooperation with the  U.S. Environmental Protection Agency

SourceContribution:
Reach codes and flow direction attributes.


Title:
Geographic Names Information System Oracle Database

SourceContribution:
Names for reaches and areal water bodies.


Originator:
U.S. Geological Survey (USGS), in cooperation with the Natural Resources Conservation Service (NRCS),  and the New Hampshire Department of Environmental Services.


SourceCurrentnessReference:
Date the revision process step was completed


SourceContribution:
DRG, USGS topo, NED, DEM, DOP, local survey


# NHDFCode

Description:
Underground Conduit: Positional Accuracy = Definite


Description:
Underground Conduit: Positional Accuracy = Indefinite


Description:
Underground Conduit: Positional Accuracy = Approximate


Description:
Pipeline: Pipeline Type = Stormwater; Relationship to Surface = At or Near


Description:
Pipeline: Pipeline Type = Stormwater; Relationship to Surface = Elevated


Description:
Pipeline: Pipeline Type = Stormwater; Relationship to Surface = Underground


Description:
Pipeline: Pipeline Type = Stormwater; Relationship to Surface = Underwater


Description:
Swamp/Marsh: Hydrographic Category = Intermittent


Description:
Reservoir: Reservoir Type = Disposal; Construction Material = Earthen


Description:
Reservoir: Reservoir Type = Disposal; Construction Material = Nonearthen


Description:
Canal/Ditch: Canal/Ditch Type = Aqueduct


Description:
Dam/Weir: Construction Material = Earthen


Description:
Dam/Weir: Construction Material = Nonearthen


Description:
Swamp/Marsh: Hydrographic Category = Perennial


Description:
Lake/Pond: Hydrographic Category = Intermittent


Description:
Lake/Pond: Hydrographic Category = Perennial


Description:
Lake/Pond: Hydrographic Category = Intermittent; Stage = High Water Elevation


Description:
Lake/Pond: Hydrographic Category = Intermittent; Stage = Date of Photography


Description:
Lake/Pond: Hydrographic Category = Perennial; Stage = Average Water Elevation


Description:
Lake/Pond: Hydrographic Category = Perennial; Stage = Normal Pool


Description:
Lake/Pond: Hydrographic Category = Perennial; Stage = Date of Photography


Description:
Lake/Pond: Hydrographic Category = Perennial; Stage = Spillway Elevation


Description:
Inundation Area: Inundation Control Status = Not Controlled


Description:
Inundation Area: Inundation Control Status = Controlled


Description:
Inundation Area: Inundation Control Status = Controlled; Stage = Flood Elevation


Description:
Pipeline: Pipeline Type = Aqueduct; Relationship to Surface = At or Near


Description:
Pipeline: Pipeline Type = Aqueduct; Relationship to Surface = Elevated


Description:
Pipeline: Pipeline Type = Aqueduct; Relationship to Surface = Underground


Description:
Pipeline: Pipeline Type = Aqueduct; Relationship to Surface = Underwater


Description:
Pipeline: Pipeline Type = General Case; Relationship to Surface = At or Near


Description:
Pipeline: Pipeline Type = General Case; Relationship to Surface = Elevated


Description:
Pipeline: Pipeline Type = General Case; Relationship to Surface = Underground


Description:
Pipeline: Pipeline Type = General Case; Relationship to Surface = Underwater


Description:
Pipeline: Pipeline Type = Penstock; Relationship to Surface = At or Near


Description:
Pipeline: Pipeline Type = Penstock; Relationship to Surface = Elevated


Description:
Pipeline: Pipeline Type = Penstock; Relationship to Surface = Underground


Description:
Pipeline: Pipeline Type = Penstock; Relationship to Surface = Underwater


Description:
Reservoir: Reservoir Type = Decorative Pool


Description:
Reservoir: Reservoir Type = Tailings Pond; Construction Material = Earthen


Description:
Reservoir: Reservoir Type = Tailings Pond


Description:
Reservoir: Reservoir Type = Swimming Pool


Description:
Reservoir: Reservoir Type = Cooling Pond


Description:
Reservoir: Reservoir Type = Filtration Pond


Description:
Reservoir: Reservoir Type = Settling Pond


Description:
Reservoir: Reservoir Type = Sewage Treatment Pond


Description:
Reservoir: Reservoir Type = Water Storage; Construction Material = Nonearthen


Description:
Reservoir: Reservoir Type = Water Storage; Construction Material = Earthen; Hydrographic Category = Intermittent


Description:
Reservoir: Reservoir Type = Water Storage; Construction Material = Earthen; Hydrographic Category = Perennial


Description:
Reservoir: Reservoir Type = Water Storage


Description:
Reservoir: Construction Material = Earthen


Description:
Reservoir: Construction Material = Nonearthen


Description:
Reservoir: Reservoir Type = Water Storage; Hydrographic Category = Perennial


Description:
Reservoir: Reservoir Type = Evaporator; Construction Material = Earthen


Description:
Rock: Relationship to Surface = Abovewater


Description:
Rock: Relationship to Surface = Underwater


Description:
Special Use Zone: Special Use Zone Type = Dump Site; Operational Status = Operational


Description:
Special Use Zone: Special Use Zone Type = Dump Site; Operational Status = Abandoned


Description:
Special Use Zone: Special Use Zone Type = Spoil Area; Operational Status = Operational


Description:
Special Use Zone: Special Use Zone Type = Spoil Area; Operational Status = Abandoned


Description:
Stream/River: Hydrographic Category = Intermittent


Description:
Stream/River: Hydrographic Category = Perennial


Description:
Sounding Datum Line: Positional Accuracy = Approximate


Description:
Sounding Datum Line: Positional Accuracy = Definite


Description:
Special Use Zone Limit: Positional Accuracy = Definite


Description:
Special Use Zone Limit: Positional Accuracy = Indefinite


Description:
Stream/River: Hydrographic Category = Ephemeral


Description:
Canal Ditch: Canal Ditch Type = Stormwater


# NHDPointEventFC

Source_DataDesc:
National Water Information System (NWIS)


