Hydrology Tools

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


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


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


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


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


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


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


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


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


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)


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


Assigns a unique ID to each stream segmentMay use to link attributes


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


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


Stream to Feature tool

Raster-to-vector conversion tool

Designed for stream networksHandles parallel stream segments properly


Raster to Polyline toolStream to Feature tool


Roadmap: Basins and watershedsSurface Fill sinksFill sinks Surface preparationSurface preparation







BasinBasin


WatershedWatershed








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


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


Roadmap: Other operationsSurface Fill sinksFill sinks Surface preparationSurface preparation







BasinBasin


WatershedWatershed








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


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


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

Hydrology Tools

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