Introduction to NHDPlus: A Framework for Advanced Water ApplicationsCindy McKayHorizon Systems Corporation

**NHDPlusAn integrated suite of application-ready, geospatial, surface water data products

First successful national attempt to integrate the NHD, NED, and WBD

Used Snapshots of NHD, NED, and WBDNational Elevation Dataset (NED)National Hydrography Dataset (NHD)Watershed Boundary Dataset (WBD)

**NHDPlus links the landscape to the mapped stream network

**NHD Stream Network andWBD Boundaries Enforced into the NEDNHD Stream Cells burned into Elevation

**NHDPlus Whats Inside?NHD Feature Classes & TablesGreatly improved 1:100K National Hydrography Dataset

NED Elevation Grids

PLUS (8 more components):Stream Network Value Added AttributesFlow Direction and Flow Accumulation GridsElevation-based CatchmentsCatchment AttributesFlowline AttributesCumulative Upstream Area AttributesFlow Volume & Velocity EstimatesNetwork Locations of USGS Flow Gaging Stations

*Stream OrderWaterbody IdentifierNetwork IdentifierLevel Path IdentifierDistance to TerminusStream Level FromNode/ToNodeHydrologic SequenceDivergence Main PathStart/Terminal FlagsQAQCed Connectivity TableNetwork Thinner NavigationAnalysisDisplay/PerformanceValue Added Attributes (VAAs)For the Stream Network

*Flow Direction Grid (FDR)A 30 meter grid in national Albers projectionEach cell points down hill to the neighboring cell with the lowest elevationSupports rain drop tools

3264128161842

**Flow Accumulation Grid (FAC)A 30 meter grid in national Albers projectionEach cell contains a count of the number of grid cells that drain to that cellUsed to generate a elevation-based synthetic stream networkUsed to guide basin delineation

*Catchments for Each Stream SegmentDefinition: The portion of the land surface that drains to a network segmentNHDPlus includes catchments in grid format and as polygons

*Catchments for Each Coastline Segment

**Catchment AttributesMean Annual Temperature (Prism - 4km)Mean Annual Precipitation (Prism - 4km)% of each of the 21 land use classifications from the 1992 National Land Cover Dataset (NLCD)Headwater Node Area

**Flowline AttributesRaw minimum/maximum elevationsSmoothed minimum/maximum elevationsSlope

**Cumulative CharacteristicsMean Annual Precip and TempNeeded for stream flow estimatesDrainage AreaNeeded for stream flow & velocity estimates21 NLCD Land Use CategoriesVery handy to have

**Flow Volume & Velocity EstimatesMean Annual Flow volumeTwo Methods: Unit Runoff & VogelVelocityJobson Method

*Gage id: 01586500Station Name North Br Patapsco RiverReachcode: 02060003001478Drainage Area: 91 mi2Max Daily Flow: 3550Avg Daily Flow: 102.4

Plus many flow statisticsNetwork Locations of USGS Stream Gages

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*STEP 1

*STEP 2

*STEP 3

*STEP 4

*STEP 5

*STEP 6

*STEP 7

*Value Added AttributesTemperature&PrecipitationLand UseFlow Volume & VelocitySTEP 8

*Watershed Characterization

Main Stem: Huntsville Spring BranchStream Order: 3Stream Level: 4

Area weighted precipitation 1431.2 mmArea weighted temperature 15.3 oC

Land UseOpen Water 1%Residential 28%Commercial/Ind/Trans 9%Barren 1%Forest 33%Pasture/Hay 5%Row Crops 12%Urban/Rec Grasses 5%Wetlands 5%Other 1%

Drainage area 180.5 km2

Mean Annual Flow (UROM) 128.6 cfsMean Annual Flow (Vogel) 123.7 cfs

Mean Annual Velocity (UROM) 0.95 fpsMean Annual Velocity (Vogel) 0.87 fps

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**http://nsdi.epa.gov/waters/Click on the NHDPlus LinkQuestions?

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