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UC 2006 Tech SessionUC 2006 Tech Session11
David MaidmentSteve Kopp
Nawajish NomanDean Djokic
Louis Wasson
GIS Hydro 2006 Part 1
An Introduction to GIS and Surface Hydrology
UC 2006 Tech SessionUC 2006 Tech Session22
OutlineOutline
• Hydrology overviewHydrology overview• GIS tools and data for hydrology – the building blocksGIS tools and data for hydrology – the building blocks• GIS data models and specialized tools (ArcHydro)GIS data models and specialized tools (ArcHydro)• 10:15 Break10:15 Break• A user’s perspective on ArcHydroA user’s perspective on ArcHydro• Hydrologic modelingHydrologic modeling• Hydraulic modelingHydraulic modeling
UC 2006 Tech SessionUC 2006 Tech Session33
Water Resources OverviewWater Resources Overview
• 2 broad categories of terrestrial water2 broad categories of terrestrial water– Surface waterSurface water– GroundwaterGroundwater
• 2 broad categories of water modeling2 broad categories of water modeling– QuantityQuantity– QualityQuality
• Today’s focus Today’s focus surface water quantitysurface water quantity
UC 2006 Tech SessionUC 2006 Tech Session44
Surface Water QuantitySurface Water Quantity
• How much water is there?How much water is there?– Rainfall-runoff modeling, a type of hydrologic modeling, Rainfall-runoff modeling, a type of hydrologic modeling,
determines for a given storm on a landscape, how much water will determines for a given storm on a landscape, how much water will become runoff.become runoff.
• Where will it go?Where will it go?– Hydraulic modeling takes the quantity of water and the shape of Hydraulic modeling takes the quantity of water and the shape of
the landscape and stream channel and determines how deep the 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.water will be and what area it will cover in the event of a flood.
UC 2006 Tech SessionUC 2006 Tech Session55
Hydrologic ModelingHydrologic Modeling
• GoalGoal:: Find stream discharge, Find stream discharge, QQ, at a location for a given , at a location for a given precipitation.precipitation.
• GIS is used to summarize terrain and hydrologic GIS is used to summarize terrain and hydrologic characteristics of the watershed for input to a model.characteristics of the watershed for input to a model.
• Many ways to calculate Q.Many ways to calculate Q.– Statistical methodsStatistical methods
• USGS regression equations (NFF, StreamStats)USGS regression equations (NFF, StreamStats)
– ““Physical” modeling (rainfall-runoff models)Physical” modeling (rainfall-runoff models)• HEC-HMS (successor to HEC-1), etc.HEC-HMS (successor to HEC-1), etc.
UC 2006 Tech SessionUC 2006 Tech Session66
Hydrologic ModelingHydrologic Modeling
• Map natural processes onto software tasksMap natural processes onto software tasks• Aggregate landscape characteristics to simplifyAggregate landscape characteristics to simplify
– ““Lumped parameter model”Lumped parameter model”
UC 2006 Tech SessionUC 2006 Tech Session77
Hydraulic ModelingHydraulic Modeling
• Goal:Goal: to predict water surface elevations for the creation to predict water surface elevations for the creation of flood inundation maps.of flood inundation maps.– Also predict velocity, sedimentation, qualityAlso predict velocity, sedimentation, quality
• Input:Input: channel and floodplain geometry with hydraulic channel and floodplain geometry with hydraulic characteristics, plus discharge and initial water surface characteristics, plus discharge and initial water surface level.level.
• Output:Output: water surface elevation at each cross section and water surface elevation at each cross section and other characteristics.other characteristics.
UC 2006 Tech SessionUC 2006 Tech Session88
GIS Data for Hydrologic and GIS Data for Hydrologic and Hydraulic ModelingHydraulic Modeling
• Digital Elevation ModelDigital Elevation Model• http://seamless.usgs.gov/ http://seamless.usgs.gov/ • http://edna.usgs.gov/ http://edna.usgs.gov/
• Watershed boundariesWatershed boundaries• http://www.ncgc.nrcs.usda.gov/products/datasets/watershed/http://www.ncgc.nrcs.usda.gov/products/datasets/watershed/
• HydrographyHydrography• http://nhd.usgs.gov/ http://nhd.usgs.gov/
• SoilsSoils• http://www.ncgc.nrcs.usda.gov/products/datasets/statsgo/ http://www.ncgc.nrcs.usda.gov/products/datasets/statsgo/ • http://soildatamart.nrcs.usda.gov/ http://soildatamart.nrcs.usda.gov/
• LandcoverLandcover• http://seamless.usgs.gov/ http://seamless.usgs.gov/
• Current and historic water recordsCurrent and historic water records• http://waterdata.usgs.gov/nwis http://waterdata.usgs.gov/nwis • http://www.epa.gov/STORET/index.htmlhttp://www.epa.gov/STORET/index.html
• Climate, weather, rainfallClimate, weather, rainfall• http://www.ncdc.noaa.gov/oa/ncdc.html http://www.ncdc.noaa.gov/oa/ncdc.html • http://www.nws.noaa.gov/ndfd/ http://www.nws.noaa.gov/ndfd/
• Channel geometry (cross sections)Channel geometry (cross sections)
UC 2006 Tech SessionUC 2006 Tech Session99
Elevation DataElevation Data
• TypesTypes– DEM : Digital Elevation ModelDEM : Digital Elevation Model– DSM : Digital Surface ModelDSM : Digital Surface Model
• Data StructureData Structure– RasterRaster– TINTIN
UC 2006 Tech SessionUC 2006 Tech Session1010
Where do you get DEM data?Where do you get DEM data?
• SourcesSources– USGS DEM, NED, DTED, ETOPO30, SRTMUSGS DEM, NED, DTED, ETOPO30, SRTM– Interpolated from points and linesInterpolated from points and lines– Generated photogrammetricallyGenerated photogrammetrically– LiDARLiDAR
• Created with interpolation toolsCreated with interpolation tools– especially TOPOGRID, TopoToRaster especially TOPOGRID, TopoToRaster
• What cellsize and accuracy?What cellsize and accuracy?– Horizontal and Vertical resolution must be appropriate for the Horizontal and Vertical resolution must be appropriate for the
landscape and scale being modeled.landscape and scale being modeled.
UC 2006 Tech SessionUC 2006 Tech Session1111
• DEM construction issuesDEM construction issues– Resolution and extentResolution and extent– Projection (for hydrology - equal area)Projection (for hydrology - equal area)– Source elevation dataSource elevation data– Interpolation techniques (IDW, spline, via TIN)Interpolation techniques (IDW, spline, via TIN)
• Problems with contour inputProblems with contour input– Specialized DEM construction software/components Specialized DEM construction software/components
(ANUDEM, TOPOGRID, (ANUDEM, TOPOGRID, TopoToRasterTopoToRaster))
DEM ConstructionDEM Construction
UC 2006 Tech SessionUC 2006 Tech Session1212
Drainage SystemDrainage System
Watershed (Basin, Catchment, Contributing area) Watershed Boundaries
(Drainage Divides)
Pour Points (Outlets)
UC 2006 Tech SessionUC 2006 Tech Session1313
GIS Tools for Describing GIS Tools for Describing Surface Water MovementSurface Water Movement
DEMDEM
FLOW DIRECTION
SINK
FILL
FLOWLENGTH
FLOW ACCUMULATION
WATERSHED
SNAP POUR
DepressionlessDepressionlessDEMDEMAre there any sinks?Are there any sinks?
NoNo
YesYes
STREAM LINE
STREAM ORDER
STREAM LINKAp
ply
Th
resh
old
Ap
ply
Th
resh
old
UC 2006 Tech SessionUC 2006 Tech Session1414
Flow DirectionFlow Direction
64 128
116
8 24
32
128 128
2
2 2
2
2
2
4
4
4
8
1 1 2
1
4
2
8
4
4
8
2
1
2
1
1
1
4
1
4
4
4
16
4
878
74
72
67
69
56
71
49
58
50
69
64
53
58
44
55
37
22
38
31
48
24
68
74
61
53
47
34
21
12
16
11
19
12
46
49
ElevationElevation
Direction CodingDirection Coding
Flow DirectionFlow Direction
UC 2006 Tech SessionUC 2006 Tech Session1515
Flow AccumulationFlow Accumulation
0
0
0
1
0
1
0
2
0
0
0
0
3
0
7
0
5
20
4
0
0
1
0
0
0
2
0
4
1
7
24
35
0
2
2
0
64 128
116
8 24
32
Direction CodingDirection Coding
UC 2006 Tech SessionUC 2006 Tech Session1616
Function ProcessingFunction Processing
DEMDEM
FLOW DIRECTION
SINK
FILL
FLOWLENGTH
FLOW ACCUMULATION
WATERSHED
SNAP POUR
DepressionlessDepressionlessDEMDEMAre there any sinks?Are there any sinks?
NoNo
YesYes
STREAM LINE
STREAM ORDER
STREAM LINKAp
ply
Th
resh
old
Ap
ply
Th
resh
old
UC 2006 Tech SessionUC 2006 Tech Session1717
Creating Vector StreamsCreating Vector Streams
11 11
11 22 22
22 22 22 22
22 22
Value = No Data
NET_GRID
StreamToFeatureStreamToFeature
RasterToFeatureRasterToFeature
UC 2006 Tech SessionUC 2006 Tech Session1818
Stream LinkStream Link
• Assign a unique value to each stream Assign a unique value to each stream segment.segment.– Can be used as input to Watershed toolCan be used as input to Watershed tool
UC 2006 Tech SessionUC 2006 Tech Session1919
Stream OrderingStream Ordering
StrahlerStrahler ShreveShreve
33
11
11
11 11
1111
11
22 22
22 22
22
44
77
11
11
11
1111
1111
22
22
33
33
UC 2006 Tech SessionUC 2006 Tech Session2020
WatershedWatershed
• Delineate the contributing area to a cell or Delineate the contributing area to a cell or group of cells.group of cells.
UC 2006 Tech SessionUC 2006 Tech Session2121
SnapPourSnapPour
• Snap the “pour point” of a watershed to the cell of Snap the “pour point” of a watershed to the cell of highest flow accumulation within a neighborhood.highest flow accumulation within a neighborhood.– Prevents accidental creation of tiny watersheds on channel Prevents accidental creation of tiny watersheds on channel
side slopes.side slopes.
Snap distanceSnap distance
Cell you clicked onCell you clicked on
The cell that will be selected(cell with highest flow accumulation)The cell that will be selected(cell with highest flow accumulation)
Stream
Stream
UC 2006 Tech SessionUC 2006 Tech Session2222
Flow LengthFlow Length
• Calculate the length of the upstream or Calculate the length of the upstream or downstream flow path from each cell.downstream flow path from each cell.
UC 2006 Tech SessionUC 2006 Tech Session2323
Using the tools in ModelBuilderUsing the tools in ModelBuilder
UC 2006 Tech SessionUC 2006 Tech Session2424
DEM Errors – Sinks and SpikesDEM Errors – Sinks and Spikes
• Sinks: when sinks are (or are not) Sinks: when sinks are (or are not) sinks – lakes, depressions, …sinks – lakes, depressions, …– Global fillGlobal fill– Dealing with internal basinsDealing with internal basins– Selective fillSelective fill
• DepthDepth
• AreaArea
SinkSinkFilled sinkFilled sink
UC 2006 Tech SessionUC 2006 Tech Session2525
DEM EditingDEM Editing
• Streams: when streams are not where they Streams: when streams are not where they “should” be“should” be–Flat areas – difficulty in determining the flow patternFlat areas – difficulty in determining the flow pattern–Barriers (roads) diverting the flow pathsBarriers (roads) diverting the flow paths
• How to “model” bridges and culverts in DEMHow to “model” bridges and culverts in DEM• How to model damsHow to model dams
– Imposing the flow pattern - to burn or not to burn Imposing the flow pattern - to burn or not to burn (beware of the scale issues and artifacts – Saunders, (beware of the scale issues and artifacts – Saunders, 2000)2000)• Simple burnSimple burn• AGREEAGREE• OMNROMNR
UC 2006 Tech SessionUC 2006 Tech Session2626
DEM Editing DEM Editing (cont.)(cont.)
• Boundaries - when watershed boundaries are not Boundaries - when watershed boundaries are not where they “should” bewhere they “should” be–To fence or not to fenceTo fence or not to fence– Ineffective flow areasIneffective flow areas
UC 2006 Tech SessionUC 2006 Tech Session2727
DEM Editing DEM Editing (cont.)(cont.)
• ToolsTools–Global operatorsGlobal operators
• FillFill• Agree (burn/fence)Agree (burn/fence)• OMNR (when it becomes available)OMNR (when it becomes available)• SWFWMDSWFWMD• Custom – model builderCustom – model builder
–MicromanagementMicromanagement• DEM Editing toolsDEM Editing tools• Custom – model builderCustom – model builder
UC 2006 Tech SessionUC 2006 Tech Session2828
Enhanced Flow DirectionEnhanced Flow Direction (OMNR – Kenny & Matthews) (OMNR – Kenny & Matthews)
• Main stepsMain steps– Standard flow directions (D8)Standard flow directions (D8)– A hybridized raster/vector A hybridized raster/vector
topological analysis to assign D8 topological analysis to assign D8 flow directions to cells that intersect flow directions to cells that intersect the network.the network.
– An iterative raster single cell dilation An iterative raster single cell dilation and D8 assignment from within and D8 assignment from within water bodies to focus flow towards water bodies to focus flow towards the virtual segments.the virtual segments.
– A merging of results from steps 1, 2 A merging of results from steps 1, 2 and 3 to produce a final “enhanced and 3 to produce a final “enhanced flow direction grid”.flow direction grid”.
UC 2006 Tech SessionUC 2006 Tech Session2929
Summarizing Watershed CharacteristicsSummarizing Watershed Characteristics(Zonal Statistics)(Zonal Statistics)
• A A zonezone is all the areas/cells with the same is all the areas/cells with the same value.value.
• Calculate a statistic within the zones for each Calculate a statistic within the zones for each cell in a raster. cell in a raster.
• Input zones can be feature or raster.Input zones can be feature or raster.• Output as a raster, summary table, or chart.Output as a raster, summary table, or chart.
–Max flow length per watershedMax flow length per watershed–Average slope per watershedAverage slope per watershed–Average curve number per watershedAverage curve number per watershed
UC 2006 Tech SessionUC 2006 Tech Session3030
Zonal Overlay (cont.)Zonal Overlay (cont.)
SlopeSlope
WatershedsWatersheds
Mean Slope per WatershedMean Slope per Watershed
UC 2006 Tech SessionUC 2006 Tech Session3131
Where is this functionality?Where is this functionality?
• ArcInfo GRID FunctionsArcInfo GRID Functions• ArcView 3.x Spatial AnalystArcView 3.x Spatial Analyst
– Avenue requestsAvenue requests– Sample extensionSample extension
• ArcGIS Spatial Analyst 8.xArcGIS Spatial Analyst 8.x– HydrologyOp containing ArcObjects methodsHydrologyOp containing ArcObjects methods– Sample Toolbar on ArcObjectOnlineSample Toolbar on ArcObjectOnline– ArcHydroArcHydro data model tools data model tools
• ArcGIS Spatial Analyst 9.xArcGIS Spatial Analyst 9.x– Tools in the Spatial Analyst ToolboxTools in the Spatial Analyst Toolbox
UC 2006 Tech SessionUC 2006 Tech Session3232
Demonstration of Spatial Analyst Demonstration of Spatial Analyst Hydrology ToolsHydrology Tools