# Subbasin

HU_8_Name:
Upper Androscoggin. Maine, New Hampshire.


HU_8_Name:
Lower Androscoggin. Maine, New Hampshire.


# NHDFCode

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:
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


# 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:
Create high-resolution NHD from the Maine Office of GIS hydrography  data, which has historically been stored and managed by 1:24,000-scale  quadrangles and ArcInfo Librarian.  ArcInfo Librarian was used to  extract the hydrography library layers (streams, ponds, rivers, and  coast), append the tiles together, and merge like polygon features  together.  The 8-digit Hydrologic Unit Code (HUC) boundary was  obtained from the State NRCS office to clip features from the paneled  coverage that fell partially or entirely within the boundary.  Where  necessary, the HUC boundary was slightly modified to completely  include or exclude features that incorrectly overlapped the boundary.   Substantial alterations to the HUC boundary were confirmed on the  topographic maps and with NRCS.  DRGCLIPs and MEDOQs were used as a  reference to revise the current hydrography data by edge matching  between quadrangles and digitizing photorevised features.  Features  were modified to the DRGCLIPs and MEDOQs only where compelling evidence  of change existed.  The National Wetlands Inventory (NWI) was used to  confirm connectors through wetlands with none of the existing NWI  linework being incorporated into the NHD data.  Arcs from the  extracted coverages were grouped in order to examine the connectivity  of the dataset for flow determination.  In some cases it was necessary  to correct digitizing errors.  Using available evidence or cartographic  judgement, 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 to 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.   Feature codes (fcodes) were assigned to landmark, network, 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 point and waterbody features were also added.

AttributeAccuracyreport:
Attribute accuracy is tested by visual comparison of the source or symbolized display of digital files.  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 June 2002  extract from the Geographic Names Information System (GNIS).  The  entry and identifier for the names match those in GNIS.  The  association of each name to reaches has been interactively checked  against the June 2002 GNIS 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 amoung areas do not exist.  All areas close.  Spatial topology meets the Maine Office of GIS Data  Standards.  Label errors and node errors have been resolved.   Spatial topology is clean and free of errors.  The coverage was  built with polygon topology.

CompletenessReport:
The completeness of the data reflects the published USGS  topographic quadrangle usually, supplemented by Digital  Orthophoto Quadrangles (DOQs).  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  datasets 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 type of  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 topographic quadrangle 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, ver.2

DataSetCredit:
U.S. Geological Survey, in cooperation with U.S. Environmental  Protection Agency and Maine Office of Geographic Information  Systems

Address:
Mid-Continent Mapping Center - 1400 Independence Road


ProcessDescription:
Create high-resolution NHD from the Maine Office of GIS hydrography  data, which has historically been stored and managed by 1:24,000-scale  quadrangles and ArcInfo Librarian.  ArcInfo Librarian was used to  extract the hydrography library layers (streams, ponds, rivers, and  coast), append the tiles together, and merge like polygon features  together.  The 8-digit Hydrologic Unit Code (HUC) boundary was obtained  from the State NRCS office to clip features from the paneled coverage  that fell partially or entirely within the boundary.  Where necessary,  the HUC boundary was slightly modified to completely include or exclude  features that incorrectly overlapped the boundary.  Substantial  alterations to the HUC boundary were confirmed on the topographic  maps and with NRCS.  DRGCLIPs and MEDOQs were used as a reference to  revise the current hydrography data by edge matching between quads and digitizing photo-revised features.  Features were modified to the DRGCLIPs and MEDOQs only where compelling evidence of change existed.   The National Wetlands Inventory (NWI) was used to confirm connectors  through wetlands with none of the existing NWI linework being  incorporated into the NHD data.  Arcs from the extracted coverages  were grouped in order to examine the connectivity of the dataset for  flow determination.  In some cases it was necessary to correct  digitizing errors.  Using available evidence or cartographic judgment,  lines called connectors were added to join features that were deemed  to have flow between each other.  These features are coded with the feature type of connector.  All arcs were directed downstream and the nodes were prepared to help create artificial paths through 2-D water bodies to 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.  Feature codes (fcodes) were assigned to landmark, network,  waterbody features through a crosswalk that converts 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 point and waterbody features were also  added.

AttributeAccuracyreport:
Attribute accuracy was tested by visual comparison of the source or symbolized display of digital files.  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  June 2002 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 June 2002 Geographic Names Information System  names extract, however, operator error could in some cases  apply a name to a wrong reach.  Please report errors to either  the Maine Office of GIS or USGS.

CompletenessReport:
The completeness of the data reflects the published USGS  topographic quadrangle usually, supplemented by Digital  Orthophoto Quadrangles (DOQs).  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:
Approximate horizontal accuracy is 12 meters, assuming source data meets 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.  The data  retains the edge-matching discrepancies existing in the source.

DataSetCredit:
U.S. Geological Survey, in cooperation with U.S. Environmental Protection Agency and Maine Office of Geographic Information Systems


ProcessDescription:
Added flow relationships between subbasins and other updates as appropriate.


# NHDSourceCitation

Originator:
U.S. Geological Survey in cooperation with  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 Natural Resources Conservation Service (NRCS) and Maine Office of GIS (MEGIS)


SourceCurrentnessReference:
Date the revision process step was completed


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


Originator:
U.S. Geological Survey (USGS), in cooperation with Natural Resources Conservation Service (NRCS) and  Maine Office of GIS (MEGIS)


