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. 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. Illustration Flow_Dir = FlowDirection(Elev_Ras) Usage. Use the Input flow direction type to specify which method was used when the flow direction raster was created. Cells with a flow accumulation of 0 are local topographic highs and may be used to identify ridges. Could you please share the input flow direction raster that was used to create flow accumulation with me and I can investigate this further. In such a case, the weight raster may be a continuous raster representing average rainfall during a given storm. 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. Use the flow_direction_type parameter to specify which method was used when the flow direction raster was created. Highlights The WASI algorithm that calculates weighted flow-accumulation by considering man-made stormwater infrastructure is presented. The Flow Accumulation tool does not honour the Compression environment setting. The Flow Accumulation function calculates accumulated flow as the accumulated weight of all cells flowing into each downslope cell in the output raster. By default, this tool will use 50 percent of the available cores. Calculating the direction of flow. 1) Determine your streams You have calculated a flow accumulation grid, the basis for a stream network. Flow accumulation in its simplest form is the number of upslope cells that flow into each cell. Zellen mit einer hohen Abflussakkumulation sind Flächen konzentrierten Flusses und können verwendet werden, um Wasserlaufkanäle zu identifizieren. 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. 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 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). If the input data is smaller than 5,000 by 5,000 cells in size, fewer cores may be used. The Flow Accumulation tool supports three flow modeling algorithms while computing accumulated flow. Hydrological Processes 5: 81–100. ArcGIS can obtain the total area of flowing into this specific point, also called pour point. Cells of undefined flow direction will only receive flow; they will not contribute to any downstream flow. The Hydrology tools are used to model the flow of water across a surface. 1991. Note that you should carefully review the ArcGIS … "On the Extraction of Channel Networks from Digital Elevation Data." 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]). The accumulated flow is based on the number of total or a fraction of cells flowing into each cell in the output raster. # Description: Creates a raster of accumulated flow to each cell. For example, the expression to create a raster where the value one represents a stream network on a background of NoData could be: The Flow Accumulation tool calculates accumulated flow as the accumulated weight of all cells flowing into each downslope cell in the output raster. This video is about understanding the concept behind flow accumulation. Verwendung. "Extracting Topographic Structure from Digital Elevation Data for Geographic Information System Analysis." 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. The Flow Accumulation tool supports three flow modeling algorithms while computing accumulated flow. The Flow Accumulation tool supports three flow modeling algorithms while computing accumulated flow. 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. 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]). This example creates a raster of accumulated flow into each cell of an input flow direction IMG raster. The only Learn more about how Flow Accumulation works. Allen anderen Zellen wird NoData zugewiesen. The flow direction raster can be created using the Flow Direction tool. Learn more about how Flow Accumulation works. Input flow direction can be created using the D8, Multiple Flow Direction (MFD) or D-Infinity (DINF) methods. 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. Diese Methode der Ableitung der Abflussakkumulation aus einem DEM wird in Jenson und Domingue (1988) dargestellt. These are D8, Multiple Flow Direction (MFD) and D-Infinity (DINF) flow methods. Output cells with a high flow accumulation are areas of concentrated flow and can be used to identify stream channels. The mapping platform for your organization, Free template maps and apps for your industry. 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. Mit dem Werkzeug Abflussakkumulation in Verbindung mit einem Eingabe-Gewichtungs-Raster kann beispielsweise bestimmt werden, wie viel Niederschlag in einem bestimmten Abflussgebiet gefallen ist. The values for each direction from the center are the following: 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. A weight factor can optionally be applied. Output cells with a flow accumulation of zero are local topographic highs and can be used to identify ridges. When using parallel processing, temporary data will be written to manage the data chunks being processed. The input raster that shows the direction of flow out of each cell. 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. For each cell in the output raster, the result will be the number of cells that flow into it. 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 current processing cell is not considered in this accumulation. 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. (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: DINF —The input flow direction raster is of type D-Infinity (DINF). In diesem Fall kann das Gewichtungs-Raster ein kontinuierliches Raster sein, das die durchschnittliche Niederschlagsmenge während eines bestimmten Sturms darstellt. Creates a raster of flow direction from each cell to its steepest downslope neighbor. Usage. 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 accumulated flow is based on the number of total or a fraction of cells flowing into each cell in the output raster. David Tarboton: Hydrology Research Group - Terrain Analysis Using Digital Elevation Models (TauDEM) MFD —The input flow direction raster is of type Multi Flow Direction (MFD). See Analysis environments and Spatial Analyst for additional details on the geoprocessing environments that apply to this tool. Learn more about how Flow Direction works. Flow accumulation in its simplest form is the number of upslope cells that flow into each cell. The flow direction raster can be created using D8, Multiple Flow Direction (MFD) and D-Infinity methods. The output raster that shows the accumulated flow to each cell. Das Werkzeug Abflussakkumulation berechnet die Abflussakkumulation als kumulierte Gewichtung aller Zellen, die in tiefer gelegene Zellen im Ausgabe-Raster fließen. 1988. In such a case, the weight raster may be a continuous raster representing average rainfall during a given storm. If no weight raster is specified, a default weight of 1 will be applied to each cell. The Flow Accumulation tool calculates accumulated flow as the accumulated weight of all cells flowing into each downslope cell in the output raster. Here is a quick overview of the steps for delineating a watershed in ArcGIS – we have detailed directions later. New software can provide more accurate hydrologic information than other commercial GIS software such as IDRISI and ArcGIS. INTEGER —The output raster will be integer type. 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). ArcGIS can compute from the DEM the direction of flow down a slope and how many cells “flow into” each cell (called flow accumulation). These are D8, Multiple Flow Direction (MFD) and D-Infinity (DINF) flow methods. Zellen mit einer Abflussakkumulation von 0 sind lokale topographische Höhen und können verwendet werden, um Bergkämme zu identifizieren. Dies wird unter Identifizieren von Wasserlaufnetzen erläutert. Flow accumulation means add all the flow entering into the particular cell. This tool supports parallel processing. DOUBLE —The output raster will be double type. A watershed is the upslope area that contributes flow to a common outlet as concentrated drainage. Then a bit of map algebra in the raster calculator yields LS. This video demonstrates how to calculate flow direction in ESRI ArcGIS. # Requirements: Spatial Analyst Extension, # Check out the ArcGIS Spatial Analyst extension license, "C:/sapyexamples/output/outflowacc02.img", Analysis environments and Spatial Analyst. This is the default. Jenson, S. K. und J. O. Domingue. 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. Mit der Spatial Analyst-Lizenz verfügbar. 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. The output raster will always be uncompressed. In order to derive actual stream, you need to decide on a threshold at which a stream is formed. This is calculated as follows: maximum_drop = change_in_z-value / distance * 100. 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. Procedure. 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). Example. 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. This example creates a raster of accumulated flow into each cell of an input flow direction Grid raster. 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. If the flow direction contains a loop, Flow Accumulation will go into an endless cycle and never finish. The output accumulation raster can be integer, floating point, or double type. How To: Convert flow accumulation lines from a DEM file to a polyline shapefile in ArcMap Summary. The Parallel processing with Spatial Analyst help topic has more details on this capability and how to configure it. The input flow direction raster can be of type D8, Multi Flow Direction (MFD) or D-Infinity (DINF). The direction of flow is determined by the direction of steepest descent, or maximum drop, from each cell. You can control the number of cores the tool uses with the Parallel processing factor environment. Output cells with a high flow accumulation are areas of concentrated flow and can be used to identify stream channels. The type of input flow direction raster between these three influences how the Flow Accumulation tool partitions and accumulates flow in each cell. Eine analytische Methode der Bestimmung eines entsprechenden Schwellenwertes für die Wasserlaufnetzbegrenzung wird in Tarboton et al. Dies kann auch als die Niederschlagsmenge bezeichnet werden, die auf der Oberfläche auf höher gelegenen Flächen von den einzelnen Zellen auftraf. 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. 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. Cells of undefined flow direction will only receive flow; they will not contribute to any downstream flow. In general, Flow Accumulation value (at pour point A) = cell count of Watershed for pour point A - 1. 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