FLORIDA GEOGRAPHIC DATA LIBRARY DOCUMENTATION
VERSION 2005

TITLE: NATIONAL HYDROGRAPHY DATASET (NHD) - REACHES

Geodataset Name:      NHDRCH
Geodataset Type:      SHAPE
Geodataset Feature:   LINE

GENERAL DESCRIPTION:

This dataset contains the spatial extent of reaches for the National 
Hydrography Dataset (NHD) in the State of Florida. The lines are features 
that comprise the surface water drainage network and coastline-stream/river,
canal/ditch, artificial path,connector, and pipeline. The lines representing 
networkfeatures, through which water flows in a known direction, are 
oriented in the direction of flow. The lines representing coastlines are 
usually oriented so that the sea or ocean is to the right. 
DATA SOURCE(S):                   United States Geological Survey 
SCALE OF ORIGINAL SOURCE MAPS:    1:100,000
DATE OF AUTOMATION OR SOURCE:     1999
GEODATASET EXTENT:                State of Florida
FEATURE ATTRIBUTE TABLES:
Datafile Name: NHDRCH.DBF

ITEM NAME   WIDTH    TYPE     PRECISION

SHAPE         9     SHAPELINE    0
COM_ID       10     LONG         0
RCH_CODE     14     CHARACTER    0
RCH_DATE      8     CHARACTER    0
LEVEL         5     DECIMAL      0
METERS       12     FLOAT        0
GNIS_ID       8     CHARACTER    0
NAME         99     CHARACTER    0
FTYPE        24     CHARACTER    0
FCODE         5     DECIMAL      0
DESC         130    CHARACTER    0
DESCRIPT     24     CHARACTER    0 
  

FEATURE ATTRIBUTE TABLES CODES AND VALUES:

ITEM            ITEM DESCRIPTION

SHAPE            Data attribute inherent to the ESRI shapefile format,
                 which defines the data as a point, polyline, or polygon.

COM_ID           Unique common identifier of the NHD feature or reach

RCH_CODE         Unique identifier, 14 digit code with two parts
                 First 8 digits - Hydrologic Unit, code for the cataloging unit in 
                                  which the reach exists. Hydrologic units provide
                                  a systematic means of identifying and subdividing
                                  river-basin units. Cataloging unit is the fourth-
                                  level subdivision of hydrologic units.
                 Last 6 digits  - Assigned in sequential order, and arbitrarily
                                  among the reaches. 

RCH_DATE         Date the RCH_CODE was assigned

LEVEL             Stream level which is the main path to which a transport reach
                  belongs. It has a value range of 1 to 99 and the value -9998 
                  for "unspecified".
                 
METERS           Length of the NHD feature, in meters

GNIS_ID          GNIS identifier of the waterbody reach name. A "blank" means that
                 the name is not populated. GNIS is an 8-digit code from the
                 Geographic Names Information System developed by the USGS and the 
                 USBGN. The Federally recognized name of each feature described in 
                 the data base is identified, and references are made to a
                 feature's location by State, county, and geographic coordinates.

NAME             Text of the reach name. A "blank" means that the name is not 
                 populated.

FTYPE            Features are classified by type. These feature types provide the
                 basic description of the features. Each type has a name and a definition. 
                 STREAM/RIVER - A body of flowing water.
                 LAKE/POND - A standing body of water with a predominantly natural shoreline surrounded by land.
                 CANAL/DITCH - An artificial open waterway constructed to transport water, to irrigate or drain land,
                               to connect two or more bodies of water, or to serve as a waterway for watercraft.
                 CONNECTOR - A known, but nonspecific, connection between two nonadjacent network segments.
                 ARTIFICIAL PATH - An abstraction to facilitate hydrologic modeling through open water bodies and along
                                  coastal and Great Lakes shorelines and to act as a surrogate for lakes and other
                                  water bodies.
                 PIPELINE - A closed conduit, with pumps, valves and control devices, for conveying fluids, gases, or 
                            finely divided solids.
                  
FCODE            A five-digit feature code encodes the feature type and combinations of characteristics and values that
                 can be assigned to a type. The first three digits encode the feature type, and the last two digits
                 encode a set of characteristics and values. The general format of the feature code is FFFCC, in which 
                 FFF is the three-digit code for a feature type. CC is the two-digit code for a combination of values
                 for characteristics associated with a feature type. If only the feature type is identified, these last
                 two digits are assigned the value "0".

DESC             The description field uses a single character string to encode one or more characteristics and values
                 for each feature code. The general format of the character string is characteristic|value, in which 
                 "characteristic" is the name of the characteristic. The vertical line character ("|") separates the
                 characteristic and value. "Value" is the value of the characteristic for the feature code.

DESCRIPT         FGDL added item based on the item FTYPE

USER NOTES:

Please note that the NHD is designed to have many users nation wide
that use as well as update the dataset. By using the data set in shapefile
format it will no longer be possible to update the NHD. For information on 
how you can take part in the updating of NHD data, or how to get the latest
version, see their website: http://nhd.usgs.gov
The NHDRCH dataset is a combination of the Drain and Reach datasets taken
from the NHD. The two datasets were nearly identical so the attributes from
the Reach dataset was joined to the Drain dataset to form NHDRCH. In order 
to get flow direction information it is necessary to link the flow table 
to NHDRCH.shp. This table needs to be linked based on the following:
For incoming flow:
link "COM_ID" (NHDRCH.shp) to "COM_ID_2" (flow table)
For outgoing flow:
link "COM_ID" (NHDRCH.shp) to "COM_ID_1" (flow table)
more information on this process can be found at http://nhd.usgs.gov/techref.html
The National Hydrography Dataset (NHD) is a feature-based database that
interconnects and uniquely identifies the stream segments or reaches that
comprise the nations surface water drainage system. It is based initially on
the content of the U.S. Geological Survey 1:100,000-scale Digital Line Graph
(DLG) hydrography data, integrated with reach-related information from the U.S.
Environmental Protection Agency Reach File Version 3.0 (RF3). More
specifically, it contains reach codes for networked features and isolated
lakes, flow direction, names, stream level, and centerline representations for
areal water bodies. Reaches are also defined to represent waterbodies and the
approximate shorelines of the Great Lakes, the Atlantic and Pacific Oceans, and
the Gulf of Mexico. The NHD also incorporates the National Spatial Data
Infrastructure framework criteria set out by the Federal Geographic Data
Committee.
The National Hydrography Dataset combines elements of the DLG and RF3: spatial
accuracy and comprehensiveness from the DLG and network relationships, names,
stream level, and a unique identifier (reach code) for surface water features
from RF3. The NHD supersedes DLG and RF3 by incorporating them, not by
replacing them. Users of DLG and RF3 will find the National Hydrography Dataset
both familiar and greatly expanded and refined. The NHD provides a national
framework for assigning reach addresses to water-related entities, such as
industrial dischargers, drinking water supplies, fish habitat areas, wild and
scenic rivers. Reach addresses establish the locations of these entities
relative to one another within the NHD surface water drainage network in a
manner similar to street addresses. Once linked to the NHD by their reach
addresses, the upstream/downstream relationships of these water-related
entities and any associated information about them can be analyzed using
software tools ranging from spreadsheets to geographic information systems
(GIS). GIS can also be used to combine NHD-based network analysis with other
data layers, such as soils, land use and population, to help better understand
and display their respective effects upon one another. Furthermore, because the
NHD provides a nationally consistent framework for addressing and analysis,
water-related information linked to reach addresses by one organization
(national, state, local) can be shared with other organizations and easily
integrated into many different types of applications to the benefit of all. The
National Hydrography Dataset is designed to provide comprehensive coverage of
hydrologic data for the U.S. While initially based on 1:100,000-scale data, the
NHD is designed to incorporate - and encourage the development of -
higher-resolution data required by many users. It will facilitate the improved
integration of water-related data in support of the application requirements of
a growing national user community and will enable shared maintenance and
enhancement.
For further research of NHD item definitions go to the "National Hydrology Dataset, 
Contents and Concepts" at:
http://nhd.usgs.gov/chapter1/index.html#_toc474479742
Certain scale datasets are not suitable for some project, analysis, or modelling 
purposes.  Please be sure you are using the best available data. 

1:24000 scale datasets are recommended for projects that are at the county
level.  1:24000 data should NOT be used for high accuracy base mapping such as
property parcel boundaries.

1:100000 scale datasets are recommended for projects that are at the
multi-county or regional level.

1:250000 scale datasets are recommended for projects that are at the regional or
state level or larger.

Vector datasets with no defined scale or accuracy should be considered suspect.
Make sure you are familiar with your data before using it for projects or
analyses.  Every effort has been made to supply the user with data
documentation.  For additional information, see the References section and the
Data Source Contact section of this documentation.  For more information
regarding scale and accuracy, see our web pages at:

http://www.geoplan.ufl.edu/education.html
These data are based on interpretation of available information and should
not be construed as legally binding.

FGDL QUALITY ASSURANCE STATUS:

-Reprojected data to FGDL Albers HPGN (See "Map Projection Parameters" below)
-Upcased all character records
-Joined NHD.drain to NHD.reach
-Changed original file name from "nhd" to "nhdrch"
-Joined shapefile with FCODE table
-Renamed DESCRIPT field to DESC
-DESCRIPT item was added based on the item FTYPE
-Dropped old internal coverage items: RCH#, RCH_ID
-Converted coverage to shapefile
-Clipped shapefile to State of Florida

REFERENCES:


The United States Geological Survey and 
The United States Environmental Protection Agency

DATA LINEAGE SUMMARY:

The NHD is produced by a joint effort between the Environmental Protection Agency 
(EPA) and U.S. Geological Survey (USGS). Data was downloaded by GeoPlan in coverage 
format from the USGS/NHD website (http://nhd.usgs.gov/) in June 2002. When received, 
data was in the following projection: Geographic, Datum: NAD 83, Spheroid: GRS80, 
units: Decimal Degrees. The shapefile was then clipped to the State of Florida, and 
projected to FGDL Albers HPGN.

MAP PROJECTION PARAMETERS:

Projection                           ALBERS
Units                                METERS
Datum                                HPGN
Spheroid                             GRS1980
1st standard parallel                24   0  0.000
2nd standard parallel                31  30  0.000
central meridian                    -84   0  0.000
latitude of projection's origin      24   0  0.000 
false easting (meters)               400000.00000
false northing (meters)              0.00000
00000
 0.00000

DATA SOURCES CONTACT(S):

Name:      National Mapping Division, U.S. Department of Interior, U.S. Geological Survey 
Abbr.name: USGS		
Address:   12201 Sunrise Valley Drive 
           Reston, VA 20192   USA 							
Phone:     1-888-ASK-USGS (275-8747)			
Fax: 			
Web site: NHD - http://nhd.usgs.gov/index.html 
Mapping   Division - http://mapping.usgs.gov/index.html 	
Ftp site:		                 
Email:    nhd@usgs.gov                

FGDL CONTACT:

Name:                    Florida Geographic Data Library
Abbr. Name:              FGDL
Address:                 Florida Geographic Data Library
                         431 Architecture
                         PO Box 115706
                         Gainesville, FL  32611-5706
Web site:                http://www.fgdl.org
Contact FGDL:
      Technical Support:                http://www.fgdl.org/fgdlfeed.html
      FGDL Frequently Asked Questions:  http://www.fgdl.org/fgdlfaq.html
      FGDL Mailing Lists:               http://www.fgdl.org/fgdl-l.html
      For FGDL Software:                http://www.fgdl.org/software.html