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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28
votes
7answers
18k views

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....
9
votes
2answers
6k views

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, ...
2
votes
6answers
10k views

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....
2
votes
1answer
2k views

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 ...
18
votes
3answers
2k views

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 ...
5
votes
2answers
2k views

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 ...
4
votes
1answer
1k views

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 ...
10
votes
4answers
4k views

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 ...
4
votes
1answer
3k views

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 ...
3
votes
2answers
3k views

Spatial Analysis - Calculate a cells elevation (height) above the nearest stream cell

I have searched for some ideas on how to formulate this analysis, but have come up short. I imagine there is a pretty straight forward answer; any help would be greatly appreciates. Data: DEM, 1/...
5
votes
1answer
6k views

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 ...
4
votes
1answer
318 views

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 ...
4
votes
1answer
129 views

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.
3
votes
2answers
2k views

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,...
1
vote
1answer
4k views

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 ...
35
votes
2answers
15k views

Proper workflow for LAS to DEM conversion

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, ...
5
votes
1answer
2k views

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-...
7
votes
3answers
3k views

Tracing up a stream network & tabulating attributes of polygons it passes through

I have an ArcGIS question that is either very easy or impossible (my favorite kind). I am somewhat inexperienced when it comes to dealing with network analysis, so maybe I'm missing something major ...
8
votes
2answers
370 views

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'...
7
votes
3answers
2k views

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 ...
7
votes
3answers
2k views

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 ...
4
votes
1answer
1k views

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 ...
3
votes
1answer
725 views

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 ...
5
votes
1answer
1k views

Which flow routing algorithms does ArcGis support?

Other than standard D8 are there support for multiple flow algorithms like FD8, DEMON, Dinfinity etc?
3
votes
1answer
771 views

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 ...
3
votes
1answer
642 views

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 ...
1
vote
1answer
3k views

Creating weight raster for flow accumulation in ArcGIS for Desktop?

I am studying flood flow using ArcGIS for Desktop. When creating flow accumulation in hydrology, there is a weight raster. However, İf you do not have it, the programme sets its value to 1 which is ...
6
votes
3answers
3k views

How to determine elevation drop along stream with ArcGIS Desktop?

I need to calculate(estimate) hydraulic head(elevation drop) along a single river stream in order to find potential site for small hydropower plant. I have a DEM with 20m resolution and raster and ...
6
votes
1answer
501 views

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 ...
4
votes
0answers
222 views

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 ...
4
votes
1answer
255 views

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
votes
1answer
142 views

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 ...
1
vote
0answers
712 views

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 ...
1
vote
1answer
807 views

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
1answer
175 views

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 ...