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Introduction to GIS and Hydrology. Steve Kopp ESRI Dean Djokic ESRI Al Rea USGS. Outline. Hydrology overview Data GIS tools for hydrology – the building blocks GIS data models and specialized tools Hydrologic modeling Hydraulic modeling Overview of NHD-Plus. Water Resources Overview.

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Introduction to gis and hydrology l.jpg

Introduction to GIS and Hydrology

Steve Kopp ESRI

Dean Djokic ESRI

Al Rea USGS


Outline l.jpg
Outline

  • Hydrology overview

  • Data

  • GIS tools for hydrology – the building blocks

  • GIS data models and specialized tools

  • Hydrologic modeling

  • Hydraulic modeling

  • Overview of NHD-Plus


Water resources overview l.jpg
Water Resources Overview

  • 2 broad categories of water

    • Surface water

    • Groundwater

  • 2 broad categories of water modeling

    • Quantity

    • Quality

  • Today’s focus surface water quantity


Surface water quantity l.jpg
Surface Water Quantity

  • How much water is there?

    • Rainfall runoff modeling, a type of hydrologic modeling, determines for a given storm on a landscape, how much water will become runoff.

  • Where will it go?

    • Hydraulic modeling takes the quantity of water and the shape of the landscape and stream channel and determines how deep the water will be and what area it will cover in the event of a flood.


Hydrologic modeling l.jpg
Hydrologic Modeling

  • Goal: Find stream discharge, Q, at a location for a given precipitation.

  • GIS is used to summarize terrain and hydrologic characteristics of the watershed for input to a model.

  • Many ways to calculate Q.

    • Statistical methods

      • USGS regression equations (NFF, StreamStats)

    • “Physical” modeling (rainfall-runoff models)

      • HEC-HMS (successor to HEC-1), TR-20, etc.


Hydrologic modeling6 l.jpg
Hydrologic Modeling

  • Map natural processes onto software tasks

  • Aggregate landscape characteristics to simplify

    • “Lumped parameter model”


Hydraulic modeling l.jpg
Hydraulic Modeling

  • Goal: to predict water surface elevations for the creation of flood inundation maps.

    • Also velocity, sedimentation, quality

  • Input: channel and floodplain geometry with hydraulic characteristics, plus discharge and initial water surface level.

  • Output: water surface elevation at each cross section and other characteristics.


Gis data for hydrologic and hydraulic modeling l.jpg
GIS Data for Hydrologic and Hydraulic Modeling

  • Digital Elevation Model

    • http://seamless.usgs.gov/

    • http://edna.usgs.gov/

  • Watershed boundaries

    • http://www.ncgc.nrcs.usda.gov/products/datasets/watershed/

  • Hydrography

    • http://nhd.usgs.gov/

  • Soils

    • http://www.ncgc.nrcs.usda.gov/products/datasets/statsgo/

    • http://soildatamart.nrcs.usda.gov/

  • Landcover

    • http://seamless.usgs.gov/

  • Current and historic water records

    • http://waterdata.usgs.gov/nwis

    • http://www.epa.gov/STORET/index.html

  • Climate, weather, rainfall

    • http://www.ncdc.noaa.gov/oa/ncdc.html

    • http://www.nws.noaa.gov/ndfd/

  • Channel geometry (cross sections)


  • Elevation data l.jpg
    Elevation Data

    • Types

      • DEM : Digital Elevation Model

      • DSM : Digital Surface Model

    • Data Structure

      • Raster

      • TIN


    Where do you get dem data l.jpg
    Where do you get DEM data?

    • Sources

      • USGS DEM, NED, DTED, ETOPO30, SRTM

      • Interpolated from points and lines

      • Generated photogrammetrically

      • LiDAR

    • Created with interpolation tools

      • especially TOPOGRID, TopoToRaster

    • What cellsize and accuracy?

      • Horizontal and Vertical resolution must be appropriate for the landscape and scale being modeled.


    Dem construction l.jpg
    DEM Construction

    • DEM construction issues

      • Resolution and extent

      • Projection (for hydrology - equal area)

      • Source elevation data

      • Interpolation techniques (IDW, spline, via TIN)

        • Problems with contour input

      • Specialized DEM construction software/components (ANUDEM, TOPOGRID, TopoToRaster)


    Dem construction continued l.jpg
    DEM Constructioncontinued

    • Hydrologically correct DEM

      • Sinks

        • Do not fill in the Great Salt Lake

      • Streams in the correct place?

        • To burn or not to burn

      • Watershed boundaries in the correct place?

        • To fence or not to fence


    Drainage system l.jpg

    Watershed (Basin, Catchment, Contributing area)

    Watershed Boundaries (Drainage Divides)

    Pour Points (Outlets)

    Drainage System


    Gis tools for describing surface water movement l.jpg
    GIS Tools for Describing Surface Water Movement

    DEM

    FLOW ACCUMULATION

    FLOW DIRECTION

    STREAM ORDER

    Apply Threshold

    STREAM LINE

    SINK

    STREAM LINK

    No

    DepressionlessDEM

    Are there any sinks?

    FLOWLENGTH

    Yes

    FILL

    SNAP POUR

    WATERSHED


    Flow direction l.jpg

    2

    2

    2

    4

    4

    8

    2

    2

    2

    4

    4

    8

    1

    1

    2

    4

    8

    4

    1

    2

    4

    8

    128

    128

    2

    2

    1

    4

    4

    4

    1

    1

    1

    1

    4

    16

    32

    64

    128

    16

    1

    8

    4

    2

    78

    72

    69

    71

    58

    49

    74

    67

    56

    49

    46

    50

    69

    53

    44

    37

    38

    48

    64

    58

    55

    22

    31

    24

    68

    61

    47

    21

    16

    19

    74

    53

    34

    12

    11

    12

    Flow Direction

    Flow Direction

    Elevation

    Direction Coding


    Flow accumulation l.jpg

    32

    64

    128

    16

    1

    8

    4

    2

    0

    0

    0

    0

    0

    0

    0

    1

    1

    2

    2

    0

    0

    3

    7

    5

    4

    0

    0

    0

    0

    20

    0

    1

    0

    0

    0

    1

    24

    0

    0

    2

    4

    7

    35

    2

    Flow Accumulation

    Direction Coding


    Function processing l.jpg
    Function Processing

    DEM

    FLOW ACCUMULATION

    FLOW DIRECTION

    STREAM ORDER

    Apply Threshold

    STREAM LINE

    SINK

    STREAM LINK

    No

    DepressionlessDEM

    Are there any sinks?

    FLOWLENGTH

    Yes

    FILL

    SNAP POUR

    WATERSHED


    Creating vector streams l.jpg

    Value = No Data

    NET_GRID

    1

    1

    1

    2

    2

    2

    2

    2

    2

    2

    2

    Creating Vector Streams

    StreamToFeature

    RasterToFeature


    Stream link l.jpg
    Stream Link

    • Assign a unique value to each stream segment.

      • Can be used as input to Watershed


    Stream ordering l.jpg

    1

    1

    1

    1

    1

    1

    1

    1

    1

    1

    1

    2

    2

    1

    1

    1

    2

    2

    2

    3

    4

    2

    2

    3

    7

    3

    Stream Ordering

    Shreve

    Strahler


    Watershed l.jpg
    Watershed

    • Delineate the contributing area to a cell or group of cells.


    Snappour l.jpg

    Snap distance

    Stream

    Cell you clicked on

    The cell that will be selected(cell with highest flow accumulation)

    SnapPour

    • Snap the “pour point” of a watershed to the cell of highest flow accumulation within a neighborhood.

      • Prevents accidental creation of tiny watersheds on channel side slopes.


    Flow length l.jpg
    Flow Length

    • Calculate the length of the upstream or downstream flow path from each cell.


    Dem errors sinks and spikes l.jpg

    Filled sink

    Sink

    DEM Errors – Sinks and Spikes

    • Sinks: when sinks are (or are not) sinks – lakes, depressions, …

      • Global fill

      • Dealing with internal basins

      • Selective fill

        • Depth

        • Area


    Dem editing l.jpg
    DEM Editing

    • Streams: when streams are not where they “should” be

      • Flat areas – difficulty in determining the flow pattern

      • Barriers (roads) diverting the flow paths

        • How to “model” bridges and culverts in DEM

        • How to model dams

      • Imposing the flow pattern - to burn or not to burn (beware of the scale issues and artifacts – Saunders, 2000)

        • Simple burn

        • AGREE

        • OMNR


    Dem editing cont l.jpg
    DEM Editing (cont.)

    • Boundaries - when watershed boundaries are not where they “should” be

      • To fence or not to fence

      • Ineffective flow areas


    Dem editing cont27 l.jpg
    DEM Editing (cont.)

    • Tools

      • Global operators

        • Fill

        • Agree (burn/fence)

        • OMNR (when it becomes available)

        • SWFWMD

        • Custom – model builder

      • Micromanagement

        • DEM Editing tools

        • Custom – model builder


    Enhanced flow direction omnr kenny matthews l.jpg
    Enhanced Flow Direction (OMNR – Kenny & Matthews)

    • Main steps

      • Standard flow directions (D8)

      • A hybridized raster/vector topological analysis to assign D8 flow directions to cells that intersect the network.

      • An iterative raster single cell dilation and D8 assignment from within water bodies to focus flow towards the virtual segments.

      • A merging of results from steps 1, 2 and 3 to produce a final “enhanced flow direction grid”.


    Summarizing watershed characteristics zonal statistics l.jpg
    Summarizing Watershed Characteristics(Zonal Statistics)

    • A zone is all the areas/cells with the same value.

    • Calculate a statistic within the zones for each cell in a raster.

    • Input zones can be feature or raster.

    • Output as a raster, summary table, or chart.

      • Max flow length per watershed

      • Average slope per watershed

      • Average curve number per watershed


    Slide30 l.jpg

    Mean Slope per Watershed

    Watersheds

    Zonal Overlay (cont.)

    Slope


    Where is this functionality l.jpg
    Where is this functionality?

    • ArcInfo GRID Functions

    • ArcView 3.x Spatial Analyst

      • Avenue requests

      • Sample extension

    • ArcGIS Spatial Analyst 8.x

      • HydrologyOp containing VB methods

      • Sample Toolbar on ArcObjectOnline

      • Arc Hydro data model tools

    • ArcGIS Spatial Analyst 9.x

      • Tools in the Spatial Analyst Toolbox


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