Questions tagged [hydrology]
The study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability.
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Methodology for creating accurate drainage networks (and catchments) from high resolution LiDAR DEM?
This is not the first time I've stumbled over this issue; it seems that I am unable to generate a correct drainage network model and the resulting catchments from full resolution (1m cells) LiDAR data....
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2
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How to calculate stream order for vector data without a DEM? [closed]
I have a shapefile which contains the streams that were digitized from a satellite Image. I would like to calculate the stream order for this data. The data does not exactly match the DEM that I have, ...
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2
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Calculating flowpaths downstream of a point
I am assessing the flood risk posed by pipeline failure. I need to calculate the likely flow-paths for flood water downstream of critical locations along the pipeline using GIS.
I'm familiar with ...
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4
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6
answers
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Error running Arc Hydro tools function in ArcMap?
I am trying to run a function from Arc Hydro tools in ArcMap 10.1; Sink evaluation. But before it can finish it returns an error message, that, frankly, I don't understand at all.
It goes System....
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2
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2
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QGIS SAGA Channel network error: Input layers do not have the same grid extent
I am trying to follow along with this exercise using my own DEM.
I have done the first step, creating the catchment area, with no trouble. When I try to run the Channel network algorithm, however, I ...
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3
answers
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Account for bridge overpasses in a ground DEM to allow for water flow under the overpass
I have a bare earth DEM made from lidar data (A).
It works well and has passed all accuracy tests. It is used in storm surge models. The problem we are having is on underpasses. I need to allow water ...
0
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1
answer
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Population in upstream area (looping over FeatureCollection)
I want to calculate the sum of the population living in the upstream area of stations using the hydro package by gena. I think I will have to loop over the stations (using the identifier "GEMS_Stati")....
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4
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What Algorithm is used by ArcGIS Watershed tool?
Does anyone know what type of algorithm is used in the ArcGIS Watershed tool (in the Spatial Analyst package)?
Very little information given on Esri's website ... but I suspect it may be some kind of ...
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7
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1
answer
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Getting Negative Topographic Wetness Index (TWI) values in SAGA GIS?
I am getting negative topographic index wetness values in SAGA GIS - anyone else every get this?
Not all negative values, but the minimum of the TWI range is negative for some steep watersheds we are ...
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7
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3
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Calculating average stream slope at each location along stream using ArcGIS Desktop?
I'm trying to calculate the time of concentration for every point along a stream network. To calculate the time of concentration, I need the upstream channel length and channel slope.
I've been able ...
- 131
6
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1
answer
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Lowering density of GRASS r.stream.extract result?
I am fiddling with the GRASS plugin in QGIS to produce watersheds and drainage basins as well as being able to identify all the basins and watersheds leading to one point (depending where i chose to ...
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5
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1
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How to assign correct flow direction to stream network polylines?
I would like to create a map showing the results of watershed analysis as well as the resulting stream network with flow direction.
I have a stream network which has been created from the flow ...
- 20.3k
5
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1
answer
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Calculating width of unusually shaped polygon in QGIS
I have a large unusually shaped polygon of surface water within 15km radius of a site. I would like to calculate the widths of all the polygons. I would be open to calculating it at regular intervals, ...
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4
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1
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Assigning points to their respective Reaches using Stream Gradient?
This is a continuation of the question I initially posed here.
Also, I've attached a shapefile on my Drop Box account here.
I'm trying to break a stream network up into 100m reaches, assigning ...
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2
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Calculating cells elevation (height) above nearest stream cell using ArcGIS Spatial Analyst
Data:
DEM, 1/9th arc second (~10-meter), 239,891,470 cells, projected;
Streams, National Hydrology Data set, high resolutions, 9,470 features vector;
Streams, Same as above, but converted to a raster
...
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3
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2
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Arcmap 10 restrict Flow Accumulation
I am working with the Flow Accumulation tool in ArcMap 10's spatial analyst hydrology tools. This tool calculates the total number of raster cells that flow into a given cell. However, for my purposes,...
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1
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1
answer
5k
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How to indicate flow of a watershed feature?
While tracing and digitizing rivers, streams, rivulets, etc., is it possible to indicate the direction/flow in the shapefile on QGIS?
I'd like to avoid using map labels. Ideally, when done tracing, I ...
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2
answers
18k
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LAS to DEM conversion [closed]
I regularly come across LiDAR (.LAS) files with elevation data. When I do, I always struggle to find a way of converting them to a DEM for hydrological analysis. I have developed several workflows, ...
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8
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2
answers
420
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Find headwater polygons
This is a follow up question to this question.
I have a river network (multiline) and some drainage polygons (see picture below). My goal is to select only the headwater polygons (green).
With John'...
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7
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3
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2k
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Is there hydrologically correct water-course data for Africa
I was wondering if there are any hydrologically correct river-channel data available for download for Africa?
By hydrologically correct, I mean
the topology should be correct. Connected river ...
- 11k
7
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3
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4k
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Tracing up stream network & tabulating attributes of polygons it passes through
I am using ArcMap and I am somewhat inexperienced when it comes to dealing with network analysis.
I have a stream network covering a very large area & some census data. My problem is: I want to ...
- 537
6
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1
answer
1k
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Delineating coastal subbasins using SAGA GIS or GRASS in QGIS?
I'm having some problems trying to delineate watersheds using the SAGA watershed delineation tools in QGIS. I have a SRTM DEM (cell size 30 m) which I set the water cells to NULL values, following ...
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6
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1
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2k
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Generate channel network (rainwater run off) - which algorithm is the best?
I want to compute DEM for a whole country (cca 79 000 sqr. km) and I need to be hydrologically correct as much is possible. After, for this correct DEM I need to compute drainage lines of surface run-...
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1
answer
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Which flow routing algorithms does ArcGis support?
Other than standard D8 are there support for multiple flow algorithms like FD8, DEMON, Dinfinity etc?
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5
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1
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714
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Calculate Polygon Centerline with a LeastCostPath approach
I'm working on deriving the centerline of a polygon, similar to this question or this one, using a different approach. I'm 90% done with the task, but cannot reach the final step. My approach is to ...
- 963
5
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1
answer
2k
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Flow direction generated for river is incorrect
I am trying to generate a hydrologic model and I can not really proceed on the next processes. I have this problem on generating flow direction. I have already executed fill sinks and the next is flow ...
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4
votes
1
answer
283
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Limiting flow direction to D4 instead of using D8 in ArcMap?
Is there a way that I can limit flow direction to D4 instead of having it use D8?
Preferably looking for a way to do it within ArcMap.
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4
votes
1
answer
755
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Obtaining length of river upstream of points up to next point using ArcGIS Desktop?
I am carrying out a study which aim is to come up with a list of priority obstacles to fish migration to be removed based on those where more extra habitat would be created after the modification.
I ...
4
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0
answers
247
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Assigning attributes from hydrologic sinks to upstream features? [closed]
I have a large hydrology geometric network with more than 300 sinks and roughly 150 barriers. I'd like to have the SinkID added to the attributes of the barriers (some individual networks have a ...
- 181
4
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4
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2k
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Identifying highs on DEM using ArcGIS Spatial Analyst?
I have a DEM and I want to find each hill and create a polygon for its area, effectively the out closed contour that encloses the hill. I can do this visually but I'm about to work on a larger area so ...
- 1,896
4
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1
answer
267
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Watershed Tool Straight Edge Problem
I'm trying to accurately delineate a watershed into sub-basins using dams as pour points. I'm using the hydrology toolset, but I can't seem to get rid of straight edges that are along some of the ...
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4
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1
answer
2k
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How to calculate "water accumulated in each cell" using QGis?
I create channel network and catchment area from a DEM with SAGA GIS. I know that flow is starting from a cell to an other cell. Firstly, a cell is filled with water and then it is starting to flow ...
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3
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2
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Delineating large scale watershed?
I would like to do some watershed delineation at national/regional level (using SRTM-90 data).
I have experimented with r.watershed (GRASS 6.4.3) but it fell over when I tried to do big stuff.
I ...
- 505
3
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2
answers
1k
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QGIS: Saga Channel network: how to prepare SRTM data
I am trying to use the Saga toolbox (2.2.3) in QGIS (2.18) to create a channel network from SRTM data using this tutorial 1.
It works, but the result I get when using the DEM that comes with the ...
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3
votes
2
answers
414
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Forming continuous network out of discontinuous lines in ArcMap
I have river data, which consists of lines (narrow sections of streams) and polygons (wider sections of streams). I would like to have all data in line form.
First, I tried Collapse Dual Lines to ...
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3
votes
1
answer
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Calculating Mean Upslope slope, curvature, etc
I'm trying to generate rasters whose values summarize the mean value of a given parameter (slope, curvature, etc.) of the upslope terrain. I feel like this should be doable using only a flow ...
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2
votes
1
answer
618
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Flow accumulation algorithm open source code in C++ on Windows
I'm looking for flow accumulation open source implementation ( C++ or C# would do, Python no), on Windows, preferably the source code comes with Visual Studio project files so that I can just build ...
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1
answer
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How to Create a Catchment Area of a Polygon (Wetland) using DEM in QGIS or Whitebox GAT
I am looking for a way to calculate the upstream catchment area where water would flow into a given wetland.
I have delineated the boundary of a wetland (creating a polygon) and would like to ...
1
vote
1
answer
98
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How to add a column in one shapefile that is the sum of values in another shapefile?
I am trying to calculate a weighted average CN value for 500 drainage area catchments (S1-S500).
I have one file named "DA" which has S1-S500.
Name Total_Area
S1 1.5
S2 0.8
........
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1
vote
1
answer
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Recursive calculations on a river network
I have a dataset that contains network distances along a river network. This dataset was created using Topotoolbox in Matlab, with the node and segment information exported. I've been working on the ...
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1
answer
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How to derive stream order from vector network [duplicate]
I have a recently-updated extract from NHD High Resolution (updated in last 6 months) which means it hasn't been cranked through NHDPlus, and won't for many years to come, and thus has no Stream Order ...
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0
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How can we extract the stream order branch?
Actually I am new to GIS, so I don't know much about technical terminology.
I have extracted a river network but now have a problem in distinguishing the branch order of stream (from order 1 to 2, 2 ...
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1
vote
2
answers
837
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Define catchment boundaries with GIS using R
Using a DEM, I want to define catchment boundaries for a given location on a river. Basically, what area drains into this point. In ArcMap, I can do that with flowacc and other tools; but I'd like to ...
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