Questions tagged [watershed]

Use this tag when asking a question about a watershed related to GIS environment.

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103 views

Finding points of sudden large changes in stream gradient QGIS

In QGIS I am trying to divide a streams shapefile at points at where there are sudden large increases or decreases in gradient. For example at the red circle the gradient of the stream increases from ...
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0answers
62 views

Polygons merge/union using two colums values

I'm using HydroSHEDS watersheds shapefiles for a proyect. Watershed are delinated applying the rules of Pfafstetter codification. I need to merge/union the different polygons in a same shapefile. I ...
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0answers
120 views

What causes the striations in this slope map?

I have created this slope map using a 10m DEM from alabamaview.org and I just noticed it has small striations (zoom to see): What could cause this, and is it a big deal, or am I over-analyzing the ...
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0answers
219 views

Understanding Add Surface Info Tool (Average Slope) vs Slope Tool?

What is the difference between the values calculated using the slope tool vs the slope option in the add surface information tool? I am making a map that displays watershed slope (using the slope ...
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1answer
442 views

Extracting flat areas and saving them as lakes using QGIS?

I would like to extract lakes and sea from a DEM (SRTM) and save them as a separate layer. Is this possible? I have tried to extract flat areas with the Raster Calculator, but that did not work.
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1answer
405 views

Understanding Drainage Density?

I have calculated drainage density for two watershed and need to make sense of the numbers. One watershed has a drainage density of 1.08 km/km2 (area=32 sq. km and total stream length=34.436 km). The ...
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1answer
339 views

Making rivers with higher Strahler/stream order wider in QGIS?

I have a river network and the Strahler order of all rivers in it. Now I would like to create a map similar to this one http://www.hydrosheds.org/, i.e. with rivers of a higher Strahler order being ...
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1answer
115 views

Using NLCD to quantify rate of urban sprawl in a watershed

I have downloaded five datasets and would like to quantify the rate of urban sprawl in a watershed from 2001 to 2011 using NLCD. Here is the data I have: (1) NLCD 2001 to 2011 Land Cover from to ...
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229 views

What channel initiation threshold value should I use when creating a stream network for drainage density calculation?

I need to calculate drainage density for two southern AL watersheds (D’Olive and Fly Creek). What channel initiation threshold value should I use when creating the stream network? I am following ...
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0answers
350 views

ArcHydro catchment area of specific stream segment

I am given the task to create the catchment areas of specific streams/lakes. To sum it all up, I am looking to find the catchment areas for lake 1, stream, lake 2 and downstream of lake 2 all ...
4
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1answer
569 views

Does r.stream.basin still exist? GRASS-QGIS2.18.7

So I'm following steps in another topic that seems to date to January of this year and is exactly what I want to do, here's the link: Get drainage basin of a polygon and at one of the last steps in ...
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1answer
423 views

drainage basin for whole lake QGIS 2.18.7

I am currently facing a problem. Over the past week, I have been initiated to hydrology within the GIS environment and have finally successfully generated water basins (using the GRASS r.water.outlet) ...
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0answers
1k views

Using WATERSHED to delineate tree crowns in ArcGIS Desktop? [closed]

I'm trying to delineate and count trees from a DSM/DTM generated from a UAV survey. It's from a citrus grove where trees are growing in different spacing. I have developed a workflow that works for ...
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1answer
1k views

Selecting point to obtain water basin leading to it

For the past few days, I have been working on building a watershed model including drainage basins and find that I am not looking for a global watershed and basin distribution, I am looking to ...
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0answers
158 views

Error while using Watershed tool

I was trying to create watershed from a DEM that used polylines. So I converted that to raster and the raster to TIN. I delineated the TIN to fill the gaps and then returned it to raster. Then I got ...
3
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1answer
108 views

Drainage basins ignoring lake

This is my first time writing in this forum and I hope this question offers some quality of information easing a solution. Here goes. I am new in analyzing hydrology with DEMs and I have followed ...
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1answer
742 views

From DWG to Shapefile: How to extract the channels length of water courses?

I have a DWG file with the drainage system of a small town. I need to open it on ArcGIS and get the total length of the channels that are part of one of the watersheds in the city. When I convert the ...
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0answers
93 views

Adding curb/gutter and subsurface storm drain networks to watershed analysis in QGIS

I need to do a neighborhood scale drainage analysis. The analysis needs to accurately show the drainage area to each storm drain inlet. Using GRASS on QGIS 2.12.1 on OS X, I have been able to ...
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1answer
319 views

Cumulative delay function for rainfall-runoff modeling using TOPMODEL [closed]

I am trying to model rainfall-runoff using TOPMODEL in R. The TOPMODEL needs an input called "cumulative delay function". The R documentation says "Flow is routed through a delay function which ...
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2answers
125 views

Getting 8 digit watersheds for USA

Is there an alternative source for 8-digit (vector shapefiles) US watersheds? The USDA link is down and they are not responsive to my query for getting the data: https://gdg.sc.egov.usda.gov/
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1answer
264 views

Smoothing/Aggregating polygon in ArcGIS Desktop?

I have this one big polygon separated by a big gap/space like this Can anyone advise how can i edit, so that the space should be narrow, smooth without a big gap like this? What function should i ...
3
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1answer
716 views

Can't get GRASS r.water.outlet to work

I'm new to GRASS. We want to delineate a watershed using the LIDAR data we have our hands on. I tried to follow several procedures to do so, but despite all my efforts, I can only get it to select a ...
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1answer
1k views

Get drainage basin of a polygon (with QGIS, GRASS or other FOSS)

Using a polygon shapefile and a raster DEM, I'd like to find a way to get the drainage basin of a polygon area — that is, the area of all cells which drain into or through the cells contained in the ...
3
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1answer
238 views

Watershed-segmentation with orfeo toolbox

I work at the moment with the watershed-segmentation from the orfeo-toolbox. After the segmentation the pictures is split into squares. Specially the square in the middle seems to be deeper the the ...
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0answers
483 views

Getting huge range of values when using Flow Accumulation tool in ArcGIS Desktop?

I'm trying to use ArcGIS Desktop to delineate watersheds for a series of sampling sites. I've been following the protocol laid out by WhiteboxDev in General steps to create watershed boundary in ...
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1answer
120 views

Combining small watershed in a better way

I used grassgis delineated watersheds in a large area. After vectorizing the watershed raster, I ended up with a lot of tiny watersheds. "Dissolve" did help a bit, but there are about 1200 ...
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1answer
410 views

Watershed analysis using GRASS GIS

I have Contour lines shapefile which I imported that into GRASS and converted to a DEM using the IDW interpolation technique (r.surf.idw with npoints 250). Now I want watershed analysis to be done ...
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2answers
226 views

Grass tools for watershed determination are not working well in QGIS

We have been using r.watershed QGIS-Grass tools for several months now without any problem, even with different QGIS versions. However, recently the tools are getting us results with a bigger pixel ...
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2answers
291 views

How to calculate area of the output of r.water.outlet?

I wrote the following code to use r.water.outlet module in GRASS GIS: import os import sys #set up GRASS environment variables sys.path.append(os.path.join(os.environ['GISBASE'], 'etc', 'python')) ...
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1answer
404 views

Calculating mean altitude of watershed for each cell of DEM?

I have a DEM of river basin, and I need to create a raster where the cell value will be the mean elevation of watershed of this cell. I have calculated watershed area (flow accumulation x cell area). ...
2
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1answer
171 views

r.watershed basins at coast / ocean lines

I am using r.watershed to create watershed basins using a 25*25m dem. The problem I have is that basins are not always created at coast lines. I am experimenting with the parameter "minimum size of ...
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0answers
148 views

calculate flow accumulation in a river with two outlet points

I'm trying to calculate flow accumulation layer (with arcGIS) in a basin with 2 outlet points. I have used "dem reconditioning" tool to modify my dem according to a vector layer, which contains my ...
3
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1answer
912 views

How to interpolate raster data using computer vision (OpenCV)?

Background A raster file collected via LIDAR records the topography of a watershed. To properly model the watershed, the river must appear continuous without any breaks or interruptions. The roads in ...
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1answer
405 views

Automatically calculate average slope of a street segment

I'd like to be able to automatically calculate the average slope of a street segment in ArcMap (start elev - end elev / length). My map looks something like this, with street centerlines in black and ...
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0answers
78 views

Comparing areas of two raster files [closed]

I need to compare the areas of two rasters for calculating the percentage parts from another. For example, I have one raster file which shows separated agriculture fields. The value of each field is 1 ...
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1answer
136 views

How to calculate stream order in GRASS 7.0.2?

I would like to calculate Strahler's and other stream hierarchy from my input raster but I am not sure how. This manual suggests tat I should use r.stream.order command, however in version 7.0.2 "...
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1answer
586 views

How to design a flood with water elevation on a specific point?

Actually I have to know the flooding area caused by a rise of the water level due to the implementation of a dam. So I would like to know if there is an extension or any tool in QGIS or GRASS which ...
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1answer
304 views

How to define pour points from a stream network at a barrier for watershed calculations?

I'm looking for a way to check if cells from one raster file have contact or get close to cells from a second raster file. For example the blue raster is a barrier and the coloured is the flow ...
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0answers
171 views

Watershed delineation with meandering river?

I'm using ArcGIS (Hydrology toolbox) for watershed delineation for a number of pour points, and I'm running into problems with very meandering rivers on extremely flat alluvial land (Amazon basin). ...
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0answers
70 views

Ideal minimal area for watershed automatic delineation using DEM SRTM

I need to do a bunch of analysis on a city using for that, watersheds . As smaller the watersheds are, better are quality of my work. Due to the vertical accuracy of SRTM DEM, I know there are some ...
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1answer
43 views

How do I know topo layer contains DEM-altitude? ArcMap 10.3

How do I know if a topographic layer contains DEM-altitude? ArcMap 10.3
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1answer
471 views

Expression into the raster calculator to invert DEM

I've made a DEM from first pass LiDAR data which I want to invert and run watershed segmentation and basin delineation over in order to hopefully extract tree canopy outlines and heights - I'm newish ...
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0answers
322 views

Using “snap pour point” to find a watershed of specific area starting from a point [closed]

I am trying to find everything downhill of a certain point in order to create a watershed of a specific area. For example, say I have a point at (x,y), and I'm interested in creating a watershed ...
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1answer
728 views

Basin creation GRASS vs. flow direction

I have a strange behaviour in QGIS with GRASS tools. I am trying to create basins in the alp region and use he SRTM3 data. As I can see on the flow direction raster the SRTM3 data seems to act nice: ...
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0answers
386 views

Why do I get an error running Catchment Polygon Processing?

I am trying to run catchment polygon processing in ArcGIS 10.3, and this is what i get "error hresult e_fail has been returned from a call to a com component" Can you help me to debug this error?
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1answer
787 views

Calculating watershed using snap pour points?

I am trying to calculate a watershed layer and have followed instructions from this previous question: General steps to create watershed boundary in ArcGIS Spatial Analyst? I have combined all these ...
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0answers
236 views

Riparian corridor delineation in QGIS

I am trying to delineate the riparian corridors using GRASS in R. But I am having some issues. So is there a plugin in QGIS using which I can extract riparian corridors using the already available ...
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0answers
343 views

Different watersheds for same area because of “burned streams”

Im trying to analyse where water is flowing which rains down to my project area. This is the DEM I have (my project area is bordered blue, the red marks are my pour points): I learned from another ...
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0answers
49 views

grass r.watershed to larger rivers parallel lines to same stretch

I'm trying create stream channels with r.watershed grass64. However, it shows two or three parallel lines for the same stretch of river. The river is large in some parts, but is just one river. Does ...
4
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1answer
355 views

Could bridges prevent ArcMap from creating correct watersheds?

I have a very detailed DEM of a region in Northern Germany. For hours I tried creating correct watersheds but my results all look illogical. Is it possible that bridges disturb the ArcMap Tools? I ...