hydrology tools
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Copyright © 2001–2004 ESRI. All rights reserved. Working with ArcGIS Spatial Analyst
Hydrology tools
9-2Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
Lesson 9A overview
Surface hydrology toolsCreating hydrologically correct topographic surfaces
Defining flow direction over the surface
Defining stream networksAnalyzing streams
Defining drainage basins
Determining flow length and tracing rain drops
Exercise 9A
Lesson 9B: Groundwater hydrology tools
9-3Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
ArcHydro Data Model
A geospatial and temporal data model
Supports hydrologic simulation modelsIt is not itself a simulation model
Can construct a simulation model attached to ArcHydro using DLL
Can customize the behavior of ArcHydro
Hydrologic information systems
Five key areas
HydrographyHydrography4
ChannelChannel3
NetworkNetwork2
DrainageDrainage1
FlowFlow
TimeTime
Time SeriesTime Series5
9-4Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
Surface hydrology tools
Map Algebrafunctions
FlowDirectionFlowAccumulation
and so on
Hydrology Modeling toolbar in ArcMap
Hydrology Modeling toolbar in ArcMap
WatershedWatershed
Rain DropRain Drop
ArcToolboxHydrology tools
ArcToolboxHydrology tools
9-5Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
Roadmap: Surface hydrologySurface Fill sinksFill sinks Surface preparationSurface preparation
Flow AccumulationFlow Accumulation
Flow DirectionFlow Direction
Define drainage networkDefine drainage network
Stream OrderStream Order
Stream LinkStream Link
Stream to FeatureStream to Feature
BasinBasin
Snap Pour PointSnap Pour Point
WatershedWatershed
Flow LengthFlow Length
Rain drop traceRain drop trace
Stream networksStream networks
Basins and watershedsBasins and watersheds
Other operationsOther operations
Required for all surface hydrology functions
9-6Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
Topographic surfaces
Use published dataExamples: DEM, DTED
Create your ownInterpolation
Both have errors Sinks
Prepare before use Fill sinks
Use the Topo to Raster tool
9-7Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
Topo to Raster tool
Interpolates a hydrologically correct surface
PointsPoints
LakesLakes
RiversRivers
ContoursContours
BoundaryBoundary
HillshadeHillshade
Provides elevationProvides elevation
Provides elevationProvides elevation
Clipping sourceClipping source
For referenceFor reference
SinksSinks Possible inputPossible input
9-8Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
Identifying and filling sinks
SinksSurrounded by higher cells
Stop surface flow
Usually data errors
Identifying sinks Need flow direction
Filling sinksIterative process
May create new sinks
SinkSink Filled sinkFilled sink
Identify sinks
Fill sinks
ArcToolbox
9-9Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
Flow Direction tool
Created from an elevation surfaceDetermines the direction water flows through a cell
Required by all other surface hydrology tools
7878 7272
7474
7171 5858 4949
7474
7272
6767 5656 4949 4646 5050
6969 5353 4444 3737 3838 4848
242431315555 222258586464
6868 21216161 4747 19191616
121234345353 1111 1212
Elevation Elevation Flow Direction map Flow Direction map
32 64 128
16 1
8 4 2
Flow Direction Flow Direction
22 22
11
44 44 88
22
22
22 22 44 44 88
11 11 22 44 88 44
884411 22128128128128
22 4422 11 4444
111111 44 1616
9-10Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
Flow Accumulation tool
Accumulates water downhill into each cellBased on flow direction
Provide weight layer to model actual rainfall
High accumulations = streams
Flow Direction Flow Direction Flow Accumulation Flow Accumulation
0 0
0
0 0 0
0
0
1 1 2 2 0
0 3 7 5 4 0
100 2000
0 10 0 024
742 35 1
9-11Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
Creating streams
Extract high-value cells from flow accumulationCan use a conditional tool: Con or Set Null
Choose a threshold value (e.g., accumulation > 100)A low threshold creates more streams
CON(FlowAcc GT 100, 1)SETNULL(FlowAcc LT 100 , 1)
CON(FlowAcc GT 100, 1)SETNULL(FlowAcc LT 100 , 1)
9-12Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
Assigns relative ranking to stream segmentsBased on the number of tributaries
Two methods: Shreve or Strahler
Requires stream network and flow direction inputs
3
1
11 1
11
1
2 2
2 2
2
4
7
1
1
1
11
11
2
2
3
3
Shreve orderingShreve orderingStrahler orderingStrahler ordering
Stream Order tool
9-13Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
Assigns a unique ID to each stream segmentMay use to link attributes
Requires stream network and flow direction inputs
Stream Link tool
1
12
2 45 6
11
7
9
810
13Stream IDs Stream IDs
3 14
15 24
2016
1718
19
21
22 23
25 26
9-14Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
Creating basin IDs for streams
Use the Region Group toolNormally a Generalization tool
Assign unique IDs to groups of connected streams
Basin IDs Basin IDs
1
1
1 11 1
1
1
1
11
1
1 2
2 2
222
22
2
2 2
2 2
Diagonal cells NOT considered
FOURFOUR
Diagonal cells ARE considered
EIGHTEIGHT
9-15Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
Stream to Feature tool
Raster-to-vector conversion tool
Designed for stream networksHandles parallel stream segments properly
Requires stream network and flow direction inputs
Raster to Polyline toolStream to Feature tool
9-16Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
Roadmap: Basins and watershedsSurface Fill sinksFill sinks Surface preparationSurface preparation
Flow AccumulationFlow Accumulation
Flow DirectionFlow Direction
Define drainage networkDefine drainage network
Stream OrderStream Order
Stream LinkStream Link
Stream to FeatureStream to Feature
BasinBasin
Snap Pour PointSnap Pour Point
WatershedWatershed
Flow LengthFlow Length
Rain drop traceRain drop trace
Stream networksStream networks
Basins and watershedsBasins and watersheds
Other operationsOther operations
Required for all surface hydrology functions
9-17Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
Defining watersheds and basins
Find all cells that drain to a pour pointWatershed tool: You provide pour points
Basin tool: Finds its own pour points
Pour point
Watershed
The Watershed
tool
The Watershed
tool
Pour points
The Basin tool
The Basin tool
9-18Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
Snap Pour Point tool
Snaps pour point cell to high accumulation neighborLike the nearest stream cell
Use before running the Watershed tool
Snap distance
Cell you clicked on
The cell that will be selected(cell with highest flow accumulation)
Stream
9-19Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
Roadmap: Other operationsSurface Fill sinksFill sinks Surface preparationSurface preparation
Flow AccumulationFlow Accumulation
Flow DirectionFlow Direction
Define drainage networkDefine drainage network
Stream OrderStream Order
Stream LinkStream Link
Stream to FeatureStream to Feature
BasinBasin
Snap Pour PointSnap Pour Point
WatershedWatershed
Flow LengthFlow Length
Rain drop traceRain drop trace
Stream networksStream networks
Basins and watershedsBasins and watersheds
Other operationsOther operations
Required for all surface hydrology functions
9-20Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
Flow Length tool
Calculates flow length for each cell Upstream: To top of basin
Downstream: To pour point
May have a weight layer
Use to compute a basin’stime of concentration
Downstream flow length Downstream flow length
9-21Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
Performing a raindrop trace
Trace the downhill path of a raindropThe Cost Path tool returns a grid
The Hydrology Modeling toolbar returns a graphic
Use: Find where a contaminate spill will go
Downhill pathDownhill path
Source cell Source cell
9-22Working with ArcGIS Spatial AnalystCopyright © 2001–2004 ESRI. All rights reserved.
Exercise 9A overviewRun Topo to Raster
Fill surface sinks
Run Flow Direction
Run Flow Accumulation
Create a stream network
Edit stream segments
Run Basin
Run Watershed
Run Flow Length
Trace a rain drops path
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