Hydrologic Functions in ArcGIS 10.1

Arc-Hydro Tools in ArcGIS 10.1Gabriel PrezNatalia LenHerramientas de Hidrologa para la elaboracin de cuencas Hidrogrficas

IntroductionHydrologic Analysis Tools in ArcGIS contribute to the understanding of how water flows across an area and how changes in that area affect the flow. This knowledge is of great relevance in fields such as regional planning, agriculture, forestry, civil engineering, geology, and surveying, among many others.Functions of the Hydrologic Analysis ToolsModel the movement of water across a surfaceExtract hydrologic information from a Digital Elevation Model (DEM).Model drainage basins and sinks in a given area.Find and eliminate, peaks and other surface imperfections.Calculate Streams shape and lenght based on a filled raster.

Other Hydrologic Analysis ToolsArcGIS has a free extension called ArcHydro Tools which orders all the Hydrology Spatial Analyst tools and offers the possibility of additional geoprocesses for advanced users..

ArcHydro Tools not only offers Terrain preprocessing tools but also gives the possibility to do analysis in the following fields:Terrain MorphologyWatershed ProcessingNetwork analysis

ExampleGiven the mask DEM of the drainage basin of the Bogot River to its middle part, calculate and represent its hydrography using ArcGIS and Arc-Hydro Toolbox.

Define the drainage areas (sub-basins)

Identify drainage lines (rivers)

Fill SinksFills sinks and peaks in a surface raster to remove small imperfections in the elevation data.

Input: Raw DEM - rasterOutput: Filled DEM, without sinks or peaks - raster

Sinks and peaks are usual errors due to raster resolution. Thus, the sinks must be filled in order to obtain a continuous drainage network.

Fill SinksArc Hydro Tools Terrain Preprocessing DEM Manipulation Fill Sinks

Flow DirectionCreates a raster of flow direction from each cell to its steepest downslope neighbor.

Input: Filled DEM - rasterOutput: Flow Direction grid - raster

This tool takes a surface as input and outputs a raster showing the direction of flow of each cell. There are eight valid output directions relating to the eight adjacent cells into which flow could travel.

Flow DirectionArc Hydro Tools Terrain Preprocessing Flow Direction

Flow AccumulationCreates a raster of accumulated flow into each cell.

Input: Flow Direction grid - rasterOutput: Flow Accumulation grid - raster

The value of cells in the output raster is the number of cells that flow to each cell. Cells with a flow accumulation of 0 are local topography highs.

Flow AccumulationArc Hydro Tools Terrain Preprocessing Flow Accumulation

Stream Definition This tool classifies all cells with a flow accumulation greater than the user-defined threshold as cells belonging to the stream network.

The default is 1% of the largest drainage area in the entire DEM. The smaller the threshold chosen the greater the number of sub-basins delineated in a following step.

Input: Flow Accumulation grid - rasterOutput: Stream grid - raster

Computes a stream grid that contains a value of 1 for all the cells in the input flow accumulation grid that have a value greater than the given threshold.Stream DefinitionArc Hydro Tools Terrain Preprocessing Stream Definition

Stream Segmentation Assigns unique values to sections of a raster linear network between intersections.

Input: Stream grid - rasterOutput: Stream Link grid - raster

Stream grid Stream Link grid

Stream SegmentationArc Hydro Tools Terrain Preprocessing Stream Segmentation

Catchment Grid DelineationDelineates a sub-basin for every stream segment.

Inputs: Flow Direction grid and Stream Link grid - rastersOutput : Catchment grid - raster

There are as many catchment zones (subbasins) as stream links were defined in the Stream Segmentation grid.

Stream Link grid Catchment gridCatchment Grid DelineationArc Hydro Tools Terrain Preprocessing Catchment Grid Delineation

Catchment Polygon ProcessingCreates a vector layer of sub-basins using the Catchment grid computed previously.

Inputs: Catchment grid - rasterOutput : Catchment polygons - vector

Catchment grid Catchment polygonsCatchment Polygon ProcessingArc Hydro Tools Terrain Preprocessing Catchment Polygon Processing

Drainage Line ProcessingCreates a vector stream coverage. This tool vectored the stream segments previously identified.

Inputs: Stream Link grid and Flow Direction grid - raster'sOutput : Drainage Line - vector

Drainage Line Processing

Arc Hydro Tools Terrain Preprocessing Drainage Line Processing

Other useful Hydrological Analysis ToolsFlow Length. Calculates the upstream or downstream distance, or weighted distance, along the flow path of each cell.

Sink. Creates a raster identifying all sinks or areas of internal drainage.

Snap pour point. Snaps pour points to the cell of highest flow accumulation within a specified distance.

Watershed. Determines the contributing area above a set of cells in a raster. Referenceshttp://resources.arcgis.com/en/help/previous-help/index.html [Recuperado el 11 de marzo de 2014]

http://acolita.com/delimitar-automaticamente-micro-cuenca-hidrografica-especifica-en-arcgis/ [Recuperado el 11 de marzo de 2014]

HEC-GeoHMS Users Manual.

ArcGIS 10.1 Help