Technical Session Presentation Title by OAgU85U

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									                              GIS Hydro 2006 Part 1

                           An Introduction to GIS and
                               Surface Hydrology
                                 David Maidment
                                   Steve Kopp
                                 Nawajish Noman
                                  Dean Djokic
                                  Louis Wasson
1   UC 2006 Tech Session
    Outline


         • Hydrology overview
         • GIS tools and data for hydrology – the building blocks
         • GIS data models and specialized tools (ArcHydro)
         • 10:15 Break
         • A user’s perspective on ArcHydro
         • Hydrologic modeling
         • Hydraulic modeling




2   UC 2006 Tech Session
    Water Resources Overview

         • 2 broad categories of terrestrial water
                – Surface water
                – Groundwater
         • 2 broad categories of water modeling
                – Quantity
                – Quality


         • Today’s focus surface water quantity




3   UC 2006 Tech Session
    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.




4   UC 2006 Tech Session
     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), etc.




5   UC 2006 Tech Session
     Hydrologic Modeling

    • Map natural processes onto software tasks
    • Aggregate landscape characteristics to simplify
      – “Lumped parameter model”




6    UC 2006 Tech Session
    Hydraulic Modeling

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



7   UC 2006 Tech Session
    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)



8   UC 2006 Tech Session
     Elevation Data

        • Types
                – DEM : Digital Elevation Model
                – DSM : Digital Surface Model


        • Data Structure
                – Raster
                – TIN




9   UC 2006 Tech Session
      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.




10   UC 2006 Tech Session
      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)




11   UC 2006 Tech Session
      Drainage System


                    Watershed
                    (Basin, Catchment,
                    Contributing area)   Watershed Boundaries
                                         (Drainage Divides)




                                                         Pour Points
                                                         (Outlets)




12   UC 2006 Tech Session
      GIS Tools for Describing
      Surface Water Movement

                            DEM
                                                         FLOW ACCUMULATION




                                                         Apply Threshold
          FLOW DIRECTION
                                                                               STREAM ORDER

                                                                               STREAM LINE
                            SINK
                                                                               STREAM LINK

                                   No
                                        Depressionless
          Are there any sinks?
                                             DEM
                      Yes                                                  FLOWLENGTH

                            FILL                                           SNAP POUR


                                                                           WATERSHED


13   UC 2006 Tech Session
      Flow Direction

                            78 72 69 71 58 49                 2    2   2   4   4   8
                            74 67 56 49 46 50                 2    2   2   4   4   8
                            69 53 44 37 38 48                 1    1   2   4   8   4
                            64 58 55 22 31 24                 128 128 1    2   4   8
                            68 61 47 21 16 19                 2    2   1   4   4   4
                            74 53 34 12 11 12                 1    1   1   1   4   16

                                Elevation                         Flow Direction
                                                32   64 128

                                                16       1

                                                8    4   2
                                            Direction Coding
14   UC 2006 Tech Session
      Flow Accumulation

                                            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


                               32 64 128
                               16       1

                               8    4   2

                            Direction Coding
15   UC 2006 Tech Session
      Function Processing

                            DEM
                                                         FLOW ACCUMULATION




                                                         Apply Threshold
          FLOW DIRECTION
                                                                               STREAM ORDER

                                                                               STREAM LINE
                            SINK
                                                                               STREAM LINK

                                   No
                                        Depressionless
          Are there any sinks?
                                             DEM
                      Yes                                                  FLOWLENGTH

                            FILL                                           SNAP POUR


                                                                           WATERSHED


16   UC 2006 Tech Session
      Creating Vector Streams


                                    Value = No Data



                            1   1
                                      1   2   2       StreamToFeature
                            2             2   2   2
                                2     2




                                NET_GRID




                                                      RasterToFeature
17   UC 2006 Tech Session
      Stream Link


           • Assign a unique value to each stream
             segment.
                   – Can be used as input to Watershed tool




18   UC 2006 Tech Session
      Stream Ordering


                                                1   1                       1   1
                            1   1                       1   1

                                        1       2   1                       2   1
                                                                    1
                            1                           1       2
                                    2       2                           3
                                    2   2                       3   4

                                        3                           7


                                Strahler                    Shreve


19   UC 2006 Tech Session
      Watershed


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




20   UC 2006 Tech Session
      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.

                                                 Snap
                                                 distance




                                  Cell you
                                  clicked on
                                               The cell that will be selected
                                               (cell with highest flow accumulation)


21   UC 2006 Tech Session
      Flow Length

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




22   UC 2006 Tech Session
     Using the tools in ModelBuilder




23   UC 2006 Tech Session
     DEM Errors – Sinks and Spikes

     • Sinks: when sinks are (or are not)
       sinks – lakes, depressions, …
          – Global fill
                                                  sink
                                            FilledSink
          – Dealing with internal basins
          – Selective fill
                  • Depth
                  • Area




24   UC 2006 Tech Session
     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

25   UC 2006 Tech Session
     DEM Editing (cont.)


          • Boundaries - when watershed boundaries are not
            where they “should” be
                 –To fence or not to fence
                 –Ineffective flow areas




26   UC 2006 Tech Session
     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




27   UC 2006 Tech Session
     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”.




28   UC 2006 Tech Session
     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


29   UC 2006 Tech Session
                                      Zonal Overlay (cont.)
                              Slope
                                                Mean Slope per Watershed




                            Watersheds




30   UC 2006 Tech Session
      Where is this functionality?


           • ArcInfo GRID Functions
           • ArcView 3.x Spatial Analyst
                   – Avenue requests
                   – Sample extension
           • ArcGIS Spatial Analyst 8.x
                   – HydrologyOp containing ArcObjects methods
                   – Sample Toolbar on ArcObjectOnline
                   – ArcHydro data model tools
           • ArcGIS Spatial Analyst 9.x
                   – Tools in the Spatial Analyst Toolbox




31   UC 2006 Tech Session
                            Demonstration of Spatial Analyst
                                  Hydrology Tools




32   UC 2006 Tech Session

								
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