Geographic Information Systems

Questions tagged [watershed]

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

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22 views

Seeking quarternary watershed map of Eastern Ontario?

I am looking for a quarternary watershed map of Eastern Ontario. Where is the best place to look for this? I am currently using the ArcGIS Online basemap software to create my maps. I have a CSV ...
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10 views

Modeled quickflow data per pixel

community! I'm running a hydrological model called Seasonal Water Yield from InVEST, based on monthly precipitation rasters, monthly ET rasters, a land use raster and watershed shapefile. One of the ...
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23 views

What is the complexity (big / little o) of the ArcGIS watershed delineation algorithm? [closed]

I'm curious about the complexity, in terms of Big or little O notation, of watershed delineation algorithms: Does the time required to perform a watershed delineation depend on the size of the input ...
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1answer
28 views

Calculating distance between points following flow direction on ArcMap?

I delineated flow directions in a watershed on ArcMap (10m DEM). Then I want to calculate distance between two points 'following' the flow direction in each raster cell, not a straight line distance. ...
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29 views

What does the values of Watershed Accumulation, Basin, In QGIS indicates?

While performing watershed module in QGIS each output gives some value range while changing color palette. what does it actually means in accumulation , basin, stream flow. What does the value ...
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37 views

Watershed delineation by using QGIS with ifsar dtm 5m resolution of grid

I had some problems during running the channel and drainage basin with an IFSAR DTM, 5m resolution. I followed these steps, according to the guidance from website of QGIS: I reprojected the DTM to ...
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1answer
20 views

Using GageWatershed Function in TauDEM?

I have a D8 flow direction raster made from with TauDEM's D8FlowDir method and a point vector with an attribute 'id' for each. For some reason when I use these two as input in the GageWatershed ...
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30 views

Quantitatively evaluating quality of watershed delineation stream line results?

How can we quantitatively describe the quality of watershed delineation? What metrics can I use to compare the stream line differences between a few delineations using different DEMs with different ...
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25 views

Getting gridded population to resolution of land cover?

I have a population data at census tracts level and an impervious land cover. Impervious land cover is of 30 m resolution and census tracts data stored as a vector. Is there any way that I can ...
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204 views

Watersheds and Catchment delineation in Earth Engine only with included datasets

Is there a possibility to derive Watershed boundaries or catchment areas by using one or more of the integrated data sets in google earth engine? The available data sets are: WWF HydroSHEDS ...
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18 views

Why difference in delineation of watershed by two online watershed modeling tools?

I am using two online watershed delineation tools- eRAMs and Model My Watershed (MMW)- to auto delineate watersheds using water quality monitoring sondes as my outlet points. I have three pieces of ...
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1answer
59 views

Watershed a catalog RasterStack in place of RasterLayer in lidR?

I want to use watershed with lidR package on a catalog. I paste this command: rep <- "/home/lasfiles" new_ctg <- catalog(rep) lidR:::catalog_laxindex(new_ctg) opt_output_files(new_ctg) <- ...
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1answer
72 views

Tolerance setting in watershed segmentation(EBimage/lidR) in R

Can anyone here explain to me what the "tol" parameter in the watershed algorithm implemented in the BioConductor package EBImage (and lidR) does? I find the explanation in the EBImage help difficult ...
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41 views

Using minus in water drainage model

I'm doing a lab and I'm trying to understand exactly why I'm using the tool "minus". I have a raster which I'm calling "heights". I also have two rasters with water surfaces and watercourse. I have ...
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45 views

Using tool “minus” in height model?

I'm doing a lab and I'm trying to understand exactly why I'm using the tool "minus". I have a raster which I'm calling "heights". I also have two rasters with water surfaces and watercourse. I have ...
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1answer
223 views

DEM File “not found” Error when running r.watershed with Processing Toolbox in QGIS 3.4.2 with GRASS

I have downloaded a DEM from the NASA server with "SRTM Downloader". I want to find the watershed area, so I run the "r.watershed" function form the Processing Toolbox. However, I got a multi- "...
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37 views

Determining if Runoff Sinks drain to stream or drain to road?

I've tried using the linked method to determine area that drains to stream vs drains to road. For some reason when I run the watershed tool on the the raster representing stream and road features, I ...
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1answer
43 views

how can interior basins be modified in the r.watershed GRASS function?

This is a follow up question to How does "Minimum Size of Exterior Watershed Basin" work in r.watershed command in qgis 2.18.12? I understood that the threshold parameter is used to ...
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1answer
156 views

Creating catchments/basins around stream feature class using ArcGIS Desktop?

I have a reasonably accurate steam network for a watershed. This network includes the main channel, major forks, and tributaries. Each channel, fork, and tributary are individual records with single ...
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1answer
399 views

Watersheds in SAGA Fill Sinks Wang & Liu tool

I'm delineating some coastal subbasins using open source software. I have asked a similar question before (Delineating coastal subbasins using SAGA GIS or GRASS in QGIS?). I found that using SAGA Fill ...
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1answer
127 views

Large Scale Watershed Delineation

Using QGIS,I attempted Africa's watershed delineation taking the following steps: Downloaded DEM from earthexplorer USGS (GTOPO30) Created a mosaic of the downloaded DEM Reprojected the mosaic ...
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39 views

How to calculate summed pixel area of multiple classes over a grid? Google Earth Engine

I'm trying to calculate the percent area of each transition class type (using the surface water occurrence dataset from the GEE tutorials) within a .25 by .25 degree grid box in SW Alaska. Here's a ...
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1answer
556 views

DEM reconditioning?

I'm using ArcGIS Desktop 10.5 Arc Hydro Toolbox & encountered a problem while trying to delineate watersheds respectively drainage lines. The red lines indicate my obtained drainage lines, which ...
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1answer
527 views

Google Earth Engine, how to distinguish between rivers/streams and ponds/lakes in a water mask

I am trying to pull out every lake and pond in a region of SW Alaska. I have successfully identified all water features using the following code: // study area var rect = ee.Geometry.Rectangle([-168, ...
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56 views

Getting higher stream number for lower order stream in ArcGIS Desktop?

The fourth order stream is showing greater stream number then third order stream?
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1answer
380 views

How to create “AGREE Stream” for DEM Reconditioning in Arc Hydro tool?

I want to deliniate streams and watershed using SRTM DEM. for this I am using Arc Hydro tool. While performing DEM Reconditioning for DEM manipulation it asks AGREE Stream as a input. How to create ...
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55 views

How to create an inlet drainage basin layer

Using a point layer of 8,375 inlets and a DEM, how do I create an inlet drainage basin layer with contiguous basins, each delineating water drainage for and into each inlet? I used an integer DEM, ...
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2answers
172 views

How to create “roof line” for a general polygon area?

I have a polygon with an arbitrary shape ( assume that it is well-formed with no self intersection, no duplicated points etc), and I need to subdivide the polygon into sub-polygons like how one would ...
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2answers
482 views

Is D8 flow accumulation algorithm still suitable for watershed computation if terrain contains lots of flat area?

My question is inspired ( and similar) with my previous question. But this question is more concerned about the suitability of D8 ( or in general non-dispersive) flow accumulation algorithm for ...
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1answer
23 views

Why a range in area for catchments even if stream definition is set at a single size?

Using ArcHydro, I set stream definition at 5000, 20x20 cells (approx. 50 acres). I placed points at origins of each subsequent stream with batch point generation tool. Then used batch watershed ...
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2answers
141 views

Does the common flow accumulation techniques still work over flat area?

My terrain is a highly developed area--which means that It involves lots of flat area ( gradient=0) because they have been properly paved. And it involves sudden drop, such as retaining wall, or ...
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1answer
274 views

Watershed Delineation Loop - r.water.outlet resulting in NAN area while snapped

I am attempting to create multiple watershed delineations for stations within a CSV file. I have files for flow direction (raster with a cell size of 30m), flow accumulation(raster with a cell size of ...
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218 views

Creating sub-watershed within a basin

I am a beginner to QGIS. My problem is I tried to create sub-catchment within a basin by using provided point datasets (river gauge location). In total, I have 12 measuring points (i.e 12 pairs of x ...
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1answer
200 views

Calculating floodplain for river section using DEM only in ArcGIS Desktop?

I'm looking to create areas where water might go when a river floods its banks. I have a pretty good resolution DEM (5ft^2 for each "square"). I'm not looking for anything super accurate or precise ...
2
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1answer
49 views

Watershed issue

I am attempting to create a catchment of Danube. So far I have used the r.fill.dir to create a depressionless map and flow directions. Thus, I am now looking to use r.watershed to create stream ...
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94 views

Improve Catchment polygon processing result accuracy?

I use the ArcHydro Toolbox and ArcGIS 10.4 I ran through the regular steps of Filling Sinks of a DEM, Flow Direction, Flow Accumulation, Stream Definition, Stream segmentation, catchment grid ...
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3answers
547 views

Doing watershed delineation properly using ArcGIS Desktop?

I am using ArcGIS Desktop 10.2. I have the contours and the stream in AutoCAD Civil, after converting to a shapefile, I exported them in GIS, after I created the TIN from the contours below: ...
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1answer
52 views

Extracting the z-values of a stream in a watershed if I have the values of the contours

I have the z-values of the contours (physical contours) of a watershed in AutoCAD civil, but I may use them in ArcGIS 10.2 and I have already created a DEM. I need to extract the z-values for the ...
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1answer
50 views

Attributing stream segments based upon road intersections and stream confluences

I am currently working on attributing nodes along some stream polylines. The attribution is supposed to include: 1)length of the stream from it's reference point 2) the location of the node in ...
2
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1answer
412 views

r.water.outlet is returning blank raster in QGIS

I am Getting error "Ignoring point outside computation region: 77.0072,12.2529" while deliniating watershed using r.water.outlet in QGIS. What am i doing wrong?
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120 views

Sub-watershed boundary is partial overlap the admistrative boundary

I am using ArcMap 10.3 on a Windows x64 system. I would like to extract the sub-watershed for a particular area. The data I used was ASTER 30m DEM and a shapefile of my study site. The first step was ...
2
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1answer
57 views

Spatial analysis on raster in order to get watersheds of approximate 2 ha size

I'm trying to analyse a raster in order to get watersheds at approximate 2 ha size, using flow direction/accumulation. I've been using the steps outlined below, with initial conditions for cells ...
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44 views

Converting data collected at political units (eg. census tract) to new ecologically-defined units (eg. watershed)? [closed]

I have socioeconomic status (SES) data of every health authority (HA) in the province. I overlay a watershed boundary polygon on top of multiple HAs and would like to know: What is the SES of the ...
3
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1answer
284 views

calculate 3D surface area base on slope in GIS [closed]

How can I calculate 3D surface area base on slope in GIS for each morphological units in watershed? Are there any different methods?
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2answers
7k views

How to delineate watersheds in QGIS?

I am using qgis 2.14.17 with ubuntu16. Having as input data a DEM of the region and a river network. In the manual of qgis they suggest to use a toll of qgis: Catchment area (Parallel); I dont have ...
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65 views

Extracting watersheds at (arbitrary) pour points of waterways inconsistent with DEM

I am using ArcGIS 10.4.1. I am trying to extract watersheds for a number of random locations along a river network. These locations represent points where certain physio-chemical qualities of the ...
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1answer
448 views

Calculating average slope of a watershed upstream of many points in ArcGIS (upstream basin slope)

I am trying to replicate a procedure that the USGS Streamstats performs on points delineated along a stream network. They call it the "upstream basin slope" Basically, for a given point that I have ...
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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
61 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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109 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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