# how to calculate flow accumulation in arcgis

Now I am making my own algorithm and R codes that calculate flow accumulation based on flow direction, and the test of the codes and algorithm will be done in a couple of months. The Flow Accumulation tool supports three flow modeling algorithms while computing accumulated flow. In order to derive actual stream, you need to decide on a threshold at which a stream is formed. Allen anderen Zellen wird NoData zugewiesen. A sample usage of the Flow Accumulation tool with an input weight raster might be to determine how much rain has fallen within a given watershed. Mit der Spatial Analyst-Lizenz verfügbar. In such a case, the weight raster may be a continuous raster representing average rainfall during a given storm. The Flow Accumulation tool does not honour the Compression environment setting. This example creates a raster of accumulated flow into each cell of an input flow direction IMG raster. The problem is that there is no tutorial about how the implementation works in ArcGIS ... To calculate the LS factor for the RUSLE equation, first calculate flow accumulation (facc) and slope in degrees (slp). The Flow Accumulation tool supports three flow modeling algorithms while computing accumulated flow. You can control the number of cores the tool uses with the Parallel processing factor environment. These are D8, Multiple Flow Direction (MFD) and D-Infinity (DINF) flow methods. 1988. The output raster will always be uncompressed. DINF —The input flow direction raster is of type D-Infinity (DINF). In general, Flow Accumulation value (at pour point A) = cell count of Watershed for pour point A - 1. Output cells with a high flow accumulation are areas of concentrated flow and can be used to identify stream channels. Output cells with a high flow accumulation are areas of concentrated flow and can be used to identify stream channels. DOUBLE —The output raster will be double type. Das Werkzeug Abflussakkumulation berechnet die Abflussakkumulation als kumulierte Gewichtung aller Zellen, die in tiefer gelegene Zellen im Ausgabe-Raster fließen. Procedure. (Step 2) Calculate Flow Accumulation with Flow Accumulation Tool using flow direction data as the input raster, (Step 3) Calculate slope of watershed in degrees using Slope Tool using clipped watershed DEM as the input layer, and (Step 4) Copy and paste the LS-factor formula below into Raster Calculator: If you have admin privileges on your machine, you can also use a registry key (for example, [HKEY_CURRENT_USER\SOFTWARE\ESRI\Desktop10.6\Raster]). A sample usage of the Flow Accumulation tool with an input weight raster might be to determine how much rain has fallen within a given watershed. Here is a quick overview of the steps for delineating a watershed in ArcGIS – we have detailed directions later. Usage. Creates a raster of flow direction from each cell to its steepest downslope neighbor. Flow accumulation in its simplest form is the number of upslope cells that flow into each cell. The type of input flow direction raster between these three influences how the Flow Accumulation tool partitions and accumulates flow in each cell. The result of Flow Accumulation is a raster of accumulated flow to each cell, as determined by accumulating the weight for all cells that flow into each downslope cell.. Apply this threshold, by reclassifying the flow accumulation grid to 1 - where the threshold is exceeded - and to 0 - where the threshold is below. New software named the WASI surface runoff calculator, is developed and can be applied to urban and suburban areas. This is calculated as follows: maximum_drop = change_in_z-value / distance * 100. Creates a raster of accumulated flow into each cell. The flow direction raster can be created using the Flow Direction tool. The current processing cell is not considered in this accumulation. In beiden Beispielen wird allen Zellen mit mehr als 100 Zellen, die in sie abfließen, der Wert 1 zugewiesen. These are D8, Multiple Flow Direction (MFD) and D-Infinity (DINF) flow methods. ArcGIS can compute from the DEM the direction of flow down a slope and how many cells “flow into” each cell (called flow accumulation). Illustration Flow_Acc = FlowAccumulation(Flow_Dir) Usage. Learn more about how Flow Accumulation works. Calculating the flow accumulation at point O seems straight forward with a hydrologic model, but I support you in that the calculations you are trying to make are difficult. An optional input raster for applying a weight to each cell. Using a threshold raster is particularly useful when pour points do not exist and watersheds need to be generated for the entire DEM based on the junctions of a stream network that has been derived from flow accumulation. By default, this tool will use 50 percent of the available cores. 2) This is odd and I wouldn't expect the value ranges to be different for FGDB and TIFF rasters. Photogrammetric Engineering and Remote Sensing 54 (11): 1593–1600. This video is about understanding the concept behind flow accumulation. Mit dem Werkzeug Abflussakkumulation in Verbindung mit einem Eingabe-Gewichtungs-Raster kann beispielsweise bestimmt werden, wie viel Niederschlag in einem bestimmten Abflussgebiet gefallen ist. If the input data is smaller than 5,000 by 5,000 cells in size, fewer cores may be used. If you have admin privileges on your machine, you can also use a registry key (for example, [HKEY_CURRENT_USER\SOFTWARE\ESRI\Desktop10.6\Raster]). Tarboton, D. G., R. L. Bras und I. Rodriguez–Iturbe. When using parallel processing, temporary data will be written to manage the data chunks being processed. Learn more about how Flow Direction works. The Flow Accumulation tool calculates accumulated flow as the accumulated weight of all cells flowing into each downslope cell in the output raster. The output of the Flow Direction tool is an integer raster whose values range from 1 to 255. How To: Convert flow accumulation lines from a DEM file to a polyline shapefile in ArcMap Summary. "Extracting Topographic Structure from Digital Elevation Data for Geographic Information System Analysis." Die Ausgabe des Werkzeugs bezieht sich in diesem Fall auf die Niederschlagsmenge, die durch die einzelnen Zellen abfließt, wobei davon ausgegangen wird, dass der Niederschlag komplett abfließt und nicht abgefangen wurde, verdunstet und/oder transpiriert ist oder ins Grundwasser abgeflossen ist. The result of Flow Accumulation is a raster of accumulated flow to each cell, as determined by accumulating the weight for all cells that flow into each downslope cell. Usage. Die Ergebnisse von Abflussakkumulation können verwendet werden, um durch das Anwenden eines Schwellenwertes zur Auswahl von Zellen mit einer hohen Abflussakkumulation ein Wasserlaufnetz zu erstellen. New software can provide more accurate hydrologic information than other commercial GIS software such as IDRISI and ArcGIS. The result of Flow Accumulation is a raster of accumulated flow to each cell, as determined by accumulating the weight for all cells that flow into each downslope cell.. The flow direction raster can be created using D8, Multiple Flow Direction (MFD) and D-Infinity methods. Zellen mit einer hohen Abflussakkumulation sind Flächen konzentrierten Flusses und können verwendet werden, um Wasserlaufkanäle zu identifizieren. Eingabe-Raster oder Eingabe-Wert wenn Bedingung WAHR, Eingabe-Raster oder Eingabe-Wert wenn Bedingung FALSCH, Photogrammetric Engineering and Remote Sensing, Durchführen eines bedingungsabhängigen Vorgangs mit dem Werkzeug. These are D8, Multiple Flow Direction (MFD) and D-Infinity (DINF) flow methods. In diesem Fall kann das Gewichtungs-Raster ein kontinuierliches Raster sein, das die durchschnittliche Niederschlagsmenge während eines bestimmten Sturms darstellt. Zellen mit einer Abflussakkumulation von 0 sind lokale topographische Höhen und können verwendet werden, um Bergkämme zu identifizieren. This is the default. If no weight raster is provided, a weight of 1 is applied to each cell, and the value of cells in the output raster is the number of cells that flow into each cell. The only Für die zukünftige Verarbeitung ist es wichtig, dass das Wasserlaufnetz, bestehend aus einer Reihe von linearen Raster-Features, als Werte vor einem Hintergrund von NoData-Werten dargestellt wird. This tool supports parallel processing. Then a bit of map algebra in the raster calculator yields LS. In der folgenden Grafik sind im Bild oben links die Fließrichtung aus jeder Zelle und oben rechts die Anzahl der Zellen, die in jede Zelle fließen, zu sehen. For an input D8 flow direction raster, a cell is considered to have an undefined flow direction if its value in the flow direction raster is anything other than 1, 2, 4, 8, 16, 32, 64, or 128. INTEGER —The output raster will be integer type. The Flow Accumulation tool calculates accumulated flow as the accumulated weight of all cells flowing into each downslope cell in the output raster. Dies kann auch als die Niederschlagsmenge bezeichnet werden, die auf der Oberfläche auf höher gelegenen Flächen von den einzelnen Zellen auftraf. # Requirements: Spatial Analyst Extension, # Check out the ArcGIS Spatial Analyst extension license, "C:/sapyexamples/output/outflowacc02.img", Analysis environments and Spatial Analyst. To calculate in ArcGIS first calculate the SLOPE, FLOW DIRECTION then FLOW ACCUMULATION from DEM for your area (SRTM, 1 arc, is better than ASTER, seen in many published papers). If no weight raster is specified, a default weight of 1 will be applied to each cell. A weight factor can optionally be applied. The distance is calculated between cell centers. If your computer has multiple processors or processors with multiple cores, better performance may be achieved, particularly on larger datasets. A digital elevation model (DEM) is a raster representation of a continuous surface in which each cell represents the elevation at a location. The data has been through a "fill" procedure once. 1) Determine your streams You have calculated a flow accumulation grid, the basis for a stream network. If no weight raster is provided, a weight of one is applied to each cell, and the value of cells in the output raster will be the number of cells that flow into each cell. The flow accumulation map was produced using the flow direction map, which was produced from the digital elevation model (DEM) of the river Evros river basin, in the ArcGIS 10.1 software. Wenn kein Gewichtungs-Raster angegeben ist, wird eine Gewichtung von 1 auf die Zellen angewendet, und der Wert der Zellen im Ausgabe-Raster entspricht der Anzahl von Zellen, die in jede Zelle fließen. The default temp folder location will be on your local C drive. Cells with a flow accumulation of 0 are local topographic highs and may be used to identify ridges. FLOAT —The output raster will be floating point type. Note that you should carefully review the ArcGIS … Dies wird unter Identifizieren von Wasserlaufnetzen erläutert. A-D have flow criss-crossing the yellow boundary and again at any given time have a different stream flow peak than each other - largely flowing into the yellow zone. Das Werkzeug Abflussakkumulation berechnet die Abflussakkumulation als kumulierte Gewichtung aller Zellen, die in tiefer gelegene Zellen im Ausgabe-Raster fließen. D8 —The input flow direction raster is of type D8. Raster data, such as DEMs, can be converted to vector datasets to increase analytical capabilities. By applying a threshold value to the results of the Flow Accumulation function using Map Algebra (or the Con tool in geoprocessing), a stream network can be delineated. Illustration Flow_Dir = FlowDirection(Elev_Ras) Usage. Cells of undefined flow direction will only receive flow; they will not contribute to any downstream flow. Could you please share the input flow direction raster that was used to create flow accumulation with me and I can investigate this further. The Hydrology tools are used to model the flow of water across a surface. The values for each direction from the center are the following: ArcGIS can obtain the total area of flowing into this specific point, also called pour point. Jenson, S. K. und J. O. Domingue. For each cell in the output raster, the result will be the number of cells that flow into it. Calculating the direction of flow. (1991) beschrieben. The result of Flow Accumulation is a raster of accumulated flow to each cell, as determined by accumulating the weight for all cells that flow into each downslope cell. Example. The Flow Accumulation function calculates accumulated flow as the accumulated weight of all cells flowing into each downslope cell in the output raster. ArcGIS for Developers ... (GP) tool also accepts a flow accumulation threshold raster. If the flow direction contains a loop, Flow Accumulation will go into an endless cycle and never finish. Use the Input flow direction type to specify which method was used when the flow direction raster was created. See Analysis environments and Spatial Analyst for additional details on the geoprocessing environments that apply to this tool. In order to obtain the watershed delineation we will need to follow some predefined steps and obtain the Flow direction and the Flow accumulation and obtain the for each cell in the DEM the number of cells that are flowing into them. The output raster that shows the accumulated flow to each cell. Learn more about how Flow Accumulation works. Example. I am trying to run ArcGIS 10.1 flow accumulation on a 10000 x 10000 cell unsigned 8Bit integer flow model (but 80% of that is no data). This video demonstrates how to calculate flow direction in ESRI ArcGIS. David Tarboton: Hydrology Research Group - Terrain Analysis Using Digital Elevation Models (TauDEM) The direction of flow is determined by the direction of steepest descent, or maximum drop, from each cell. Verwendung. 1991. # Description: Creates a raster of accumulated flow to each cell. The accumulated flow is based on the number of total or a fraction of cells flowing into each cell in the output raster. Cells of undefined flow direction will only receive flow; they will not contribute to any downstream flow. Zum Erstellen eines Rasters, in dem der Wert 1 das Wasserlaufnetz vor dem Hintergrund von NoData-Werten darstellt, kann beispielsweise eine der folgenden Methoden verwendet werden: Eingabe-Raster oder Eingabe-Wert wenn Bedingung WAHR : 1, Eingabe-Raster oder Eingabe-Wert wenn Bedingung FALSCH : 1. The input raster that shows the direction of flow out of each cell. Flow accumulation means add all the flow entering into the particular cell. Diese Methode der Ableitung der Abflussakkumulation aus einem DEM wird in Jenson und Domingue (1988) dargestellt. MFD —The input flow direction raster is of type Multi Flow Direction (MFD). For an input D-Infinity flow direction raster, a cell is considered to have an undefined flow direction if its value in the flow direction raster is -1. The mapping platform for your organization, Free template maps and apps for your industry. Use the flow_direction_type parameter to specify which method was used when the flow direction raster was created. If the input flow direction raster is not created with the Flow Direction tool, there is a chance that the defined flow could loop. The current processing cell is not considered in this accumulation. "On the Extraction of Channel Networks from Digital Elevation Data." You can control the location of this folder by setting up a system environment variable named TempFolders and specifying the path to a folder to use (for example, E:\RasterCache). The result of Flow Accumulation is a raster of accumulated flow to each cell, as determined by accumulating the weight for all cells that flow into each downslope cell. Cells of undefined flow direction will only receive flow; they will not contribute to any downstream flow. Eine analytische Methode der Bestimmung eines entsprechenden Schwellenwertes für die Wasserlaufnetzbegrenzung wird in Tarboton et al. Calculating flow accumulation: Release 9.3 Last modified January 13, 2012: Print all topics in : "Hydrologic analysis" Related Topics Exploring Digital Elevation Models (DEM) Deriving runoff characteristics ; Creating a depressionless DEM ; Determining flow direction ; Delineating watersheds ; Hydrologic analysis sample applications; Note: This topic was updated for 9.3.1. The result of Flow Accumulation is a raster of accumulated flow to each cell, as determined by accumulating the weight for all cells that flow into each downslope cell. By applying a threshold value to the results of the Flow Accumulation tool using either the Con or Set Null tools, a stream network can be delineated. This is the default. A watershed is the upslope area that contributes flow to a common outlet as concentrated drainage. Highlights The WASI algorithm that calculates weighted flow-accumulation by considering man-made stormwater infrastructure is presented. Output cells with a flow accumulation of zero are local topographic highs and can be used to identify ridges. If no weight raster is provided, a weight of 1 is applied to each cell, and the value of cells in the output raster is the number of cells that flow into each cell. Input flow direction can be created using the D8, Multiple Flow Direction (MFD) or D-Infinity (DINF) methods. The accumulated flow is based on the number of total or a fraction of cells flowing into each cell in the output raster. Hydrological Processes 5: 81–100. Mit der Spatial Analyst-Lizenz verfügbar. For example, the expression to create a raster where the value one represents a stream network on a background of NoData could be: The input flow direction raster can be of type D8, Multi Flow Direction (MFD) or D-Infinity (DINF). Additional details on how flow accumulation is calculated. The Parallel processing with Spatial Analyst help topic has more details on this capability and how to configure it. In such a case, the weight raster may be a continuous raster representing average rainfall during a given storm. This example creates a raster of accumulated flow into each cell of an input flow direction Grid raster. The output accumulation raster can be integer, floating point, or double type. Das Ergebnis von Flow Accumulation ist ein Raster der Abflussakkumulation zu jeder Zelle, wie durch das Akkumulieren der Gewichtung für alle Zellen, die in die einzelnen tiefer gelegenen Zelle fließen, bestimmt.. 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