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.. Zellen mit nicht definierter Fließrichtung erhalten nur Fluss; sie tragen nicht zum Wasserstrom flussabwärts bei. This video demonstrates how to calculate flow direction in ESRI ArcGIS. Illustration Flow_Dir = FlowDirection(Elev_Ras) Usage. If the input data is smaller than 5,000 by 5,000 cells in size, fewer cores may be used. 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. Das Werkzeug Abflussakkumulation berechnet die Abflussakkumulation als kumulierte Gewichtung aller Zellen, die in tiefer gelegene Zellen im Ausgabe-Raster fließen. Usage. Cells of undefined flow direction will only receive flow; they will not contribute to any downstream flow. These are D8, Multiple Flow Direction (MFD) and D-Infinity (DINF) flow methods. Cells of undefined flow direction will only receive flow; they will not contribute to any downstream flow. This is the default. ArcGIS can obtain the total area of flowing into this specific point, also called pour point. This tool supports parallel processing. 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). Mit der Spatial Analyst-Lizenz verfügbar. The distance is calculated between cell centers. Creates a raster of flow direction from each cell to its steepest downslope neighbor. In such a case, the weight raster may be a continuous raster representing average rainfall during a given storm. Procedure. Verwendung. Photogrammetric Engineering and Remote Sensing 54 (11): 1593–1600. 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. A weight factor can optionally be applied. ArcGIS can compute from the DEM the direction of flow down a slope and how many cells “flow into” each cell (called flow accumulation). Output cells with a high flow accumulation are areas of concentrated flow and can be used to identify stream channels. When using parallel processing, temporary data will be written to manage the data chunks being processed. FLOAT —The output raster will be floating point type. The type of input flow direction raster between these three influences how the Flow Accumulation tool partitions and accumulates flow in each cell. Calculating the direction of flow. How To: Convert flow accumulation lines from a DEM file to a polyline shapefile in ArcMap Summary. The Flow Accumulation function calculates accumulated flow as the accumulated weight of all cells flowing into each downslope cell in the output raster. # Requirements: Spatial Analyst Extension, # Check out the ArcGIS Spatial Analyst extension license, "C:/sapyexamples/output/outflowacc02.img", Analysis environments and Spatial Analyst. This example creates a raster of accumulated flow into each cell of an input flow direction Grid raster. 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. MFD —The input flow direction raster is of type Multi Flow Direction (MFD). Zellen mit einer hohen Abflussakkumulation sind Flächen konzentrierten Flusses und können verwendet werden, um Wasserlaufkanäle zu identifizieren. 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 Accumulation tool does not honour the Compression environment setting. In order to derive actual stream, you need to decide on a threshold at which a stream is formed. 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. An optional input raster for applying a weight to each cell. 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. Diese Methode der Ableitung der Abflussakkumulation aus einem DEM wird in Jenson und Domingue (1988) dargestellt. 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. If your computer has multiple processors or processors with multiple cores, better performance may be achieved, particularly on larger datasets. The output raster that shows the accumulated flow to each cell. The flow direction raster can be created using the Flow Direction tool. 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. The output accumulation raster can be integer, floating point, or double type. Usage. The input flow direction raster can be of type D8, Multi Flow Direction (MFD) or D-Infinity (DINF). # Description: Creates a raster of accumulated flow to each cell. Output cells with a flow accumulation of zero are local topographic highs and can be used to identify ridges. If the flow direction contains a loop, Flow Accumulation will go into an endless cycle and never finish. In such a case, the weight raster may be a continuous raster representing average rainfall during a given storm. By default, this tool will use 50 percent of the available cores. The input raster that shows the direction of flow out of 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. These are D8, Multiple Flow Direction (MFD) and D-Infinity (DINF) flow methods. 1991. 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. Example. Flow accumulation means add all the flow entering into the particular cell. "On the Extraction of Channel Networks from Digital Elevation Data." The default temp folder location will be on your local C drive. This is the default. The output of the Flow Direction tool is an integer raster whose values range from 1 to 255. The flow direction raster can be created using D8, Multiple Flow Direction (MFD) and D-Infinity methods. 1988. 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. 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. 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. 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. In general, Flow Accumulation value (at pour point A) = cell count of Watershed for pour point A - 1. Cells of undefined flow direction will only receive flow; they will not contribute to any downstream flow. This is calculated as follows: maximum_drop = change_in_z-value / distance * 100. 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]). Learn more about how Flow Direction works. The direction of flow is determined by the direction of steepest descent, or maximum drop, from each cell. A watershed is the upslope area that contributes flow to a common outlet as concentrated drainage. 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. 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. Tarboton, D. G., R. L. Bras und I. Rodriguez–Iturbe. These are D8, Multiple Flow Direction (MFD) and D-Infinity (DINF) flow methods. If the input flow direction raster is not created with the Flow Direction tool, there is a chance that the defined flow could loop. Learn more about how Flow Accumulation works. The accumulated flow is based on the number of total or a fraction of cells flowing into each cell in the output raster. (1991) beschrieben. Mit der Spatial Analyst-Lizenz verfügbar. The current processing cell is not considered in this accumulation. Raster data, such as DEMs, can be converted to vector datasets to increase analytical capabilities. Here is a quick overview of the steps for delineating a watershed in ArcGIS – we have detailed directions later. Use the Input flow direction type to specify which method was used when the flow direction raster was created. New software can provide more accurate hydrologic information than other commercial GIS software such as IDRISI and ArcGIS. Eine analytische Methode der Bestimmung eines entsprechenden Schwellenwertes für die Wasserlaufnetzbegrenzung wird in Tarboton et al. Learn more about how Flow Accumulation works. The mapping platform for your organization, Free template maps and apps for your industry. Hydrological Processes 5: 81–100. Highlights The WASI algorithm that calculates weighted flow-accumulation by considering man-made stormwater infrastructure is presented. The Hydrology tools are used to model the flow of water across a surface. 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.. 1) Determine your streams You have calculated a flow accumulation grid, the basis for a stream network. Creates a raster of accumulated flow into each cell. The Flow Accumulation tool supports three flow modeling algorithms while computing accumulated flow. The output raster will always be uncompressed. Then a bit of map algebra in the raster calculator yields LS. A digital elevation model (DEM) is a raster representation of a continuous surface in which each cell represents the elevation at a location. The Flow Accumulation tool calculates accumulated flow as the accumulated weight of all cells flowing into each downslope cell in the output raster. In beiden Beispielen wird allen Zellen mit mehr als 100 Zellen, die in sie abfließen, der Wert 1 zugewiesen. Cells with a flow accumulation of 0 are local topographic highs and may be used to identify ridges. The Flow Accumulation tool supports three flow modeling algorithms while computing accumulated flow. Additional details on how flow accumulation is calculated. For example, the expression to create a raster where the value one represents a stream network on a background of NoData could be: 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. 2) This is odd and I wouldn't expect the value ranges to be different for FGDB and TIFF rasters. "Extracting Topographic Structure from Digital Elevation Data for Geographic Information System Analysis." 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. ArcGIS for Developers ... (GP) tool also accepts a flow accumulation threshold raster. 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]). DOUBLE —The output raster will be double type. 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). 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. Flow accumulation in its simplest form is the number of upslope cells that flow into each cell. Dies kann auch als die Niederschlagsmenge bezeichnet werden, die auf der Oberfläche auf höher gelegenen Flächen von den einzelnen Zellen auftraf. 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