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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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, ...
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....
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 ...
11
votes
2answers
2k views

How to cartographically represent water flow?

I am modelling water flow on steep slopes for an erosion study. You can see from the screenshot the results from the ArcGIS-based flow analysis. To produce these flow lines, I generated a ...
10
votes
4answers
9k views

Tutorial on how to model flooding using data from gauging stations along rivers in QGIS?

Can someone please direct me to a tutorial where I can learn more about how to model flooding using data from gauging stations along rivers using QGIS?
10
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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 ...
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, ...
9
votes
1answer
341 views

How to create a branch network from several input points to an unique outlet in minimizing the distances?

I am searching a way to "hydrologically" connect upstream points to a unique downstream outlet by creating an optimized stream network as pictured below... The cummulated lenght of the stream lines ...
9
votes
2answers
2k views

How can I get weighted Flow Accumulation to deal with negative values? [duplicate]

here's one I haven't seen anywhere, to my surprise. I am trying to do something a little different with Flow Accumulation, which I would think has been attempted before, but it's stumping me for now. ...
8
votes
3answers
451 views

Locate wet patches using DEM

I'm searching for a way to determine the location of wet patches, after rainfall, in a DEM. By this, I mean puddles. We are investigating the best locations to locate paths for recreational use. ...
8
votes
2answers
373 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

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 ...
7
votes
1answer
7k views

Calculate Topographic wetness index in SAGA

i am currently working on a project which involves the quantification of the wetness in certain areas. However it produces quite different results from what i expected. I'll describe the steps i have ...
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
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 ...
7
votes
1answer
2k views

Hydrology toolbox versus Arc Hydro toolbox?

I would like to do some watershed delineation research/development (at the County level) with our LIDAR generated DEM, after it is corrected, but am wondering what, if any, differences might result ...
7
votes
1answer
450 views

Is there a downloadable data source for mapping out rivers with names for the whole world?

I'd like to be able to extract rivers with their names and the flow size (not direction) for the whole world. The scale I'll be drawing it at is about 2 centimeters per 10 real world km - nothing too ...
6
votes
1answer
757 views

In hydrologic terrain analysis is there a difference between “pits”, “depressions”, and “sinks”?

In hydrologic terrain analysis is there a difference between "pits" and "depressions"? For instance, Planchon and Darboux (2002) state The usual numerical methods for removing the depressions of a ...
6
votes
5answers
7k views

Calculating Runoff / Streams using DEM in ArcGIS

I am just curious about the workflow that many of you use for runoff/stream analysis using a DEM and create a "water network" from the results in ArcGIS 10.1? I know the average rainfall for different ...
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
820 views

How to run a tool from Whitebox GAT in ArcGIS?

I have a series of tools that I need to run in ArcGIS to hydrologically condition my DEM, but the first step in this process is running the Breach Depressions tool from Whitebox GAT (I have found that ...
6
votes
1answer
521 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 ...
5
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 ...
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-...
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?
5
votes
4answers
814 views

What satellite imagery would help to show spring locations?

I've got lots of tiny streams on a hydrography shapefile. Historic texts indicate that certain ones have headwaters at "sources" or springs, and I want to try to find these. Browsing the historical ...
5
votes
3answers
476 views

Ways to determine winding topographic characteristics of a river

Are there any methods and/or technical guides on how to classify the degree of winding of river bodies? I have the following polygon layer of roughly 100,000 water bodies and would like to write an ...
5
votes
1answer
509 views

Does this ArcGIS flow accumulation example have an error?

The lower right corner of the flow accumulation example in ArcGIS Desktop's documentation has a flow accumulation value of 2. However, I only see one cell flowing into the lower right corner (the ...
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 ...
5
votes
2answers
4k views

Flow Accumulation in R

My apologies for such a general question. Is there an ArcGIS like implementation of Flow Accumulation for R? What I am trying to avoid: Using ArcGIS; Using Grass; Using RpyGEO (but will if need be) ...
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 ...
5
votes
2answers
178 views

Performing Weighted Flow Accumulation in GRASS?

I would like to calculate a weighted flow accumulation raster with GRASS. I have a DEM and a rainfall raster. I am looking to calculate the rainfall accumulated downstream. Basically, it is similar in ...
5
votes
1answer
679 views

How do I get the upstream distance to all points in a DEM from a single downstream point?

I want to get the upstream distance to all points in a DEM from a single downstream point. The goal is to create a "downstream distance to a point grid". This then would allow me to create "distance" ...
5
votes
2answers
2k views

How to display Flow Direction arrows + Burn Stream Netwok in QGIS?

I have used the automated r.watershed tool in QGIS 2.18 (GRASS plugin) to conduct a watershed analysis (basin boundaries, flow direction, flow accumulation etc). I'm stuck on the following operations:...
5
votes
1answer
290 views

HEC GeoHMS generates wrong catchment area

I am trying to define a catchment area automatically with HEC Geo HMS (ArcGIS version 10.1). My input-data is a DEM-file (raster 1m). After doing all steps in HEC Geo HMS, the catchment area (see ...
5
votes
1answer
141 views

Global Basin Delineation Across Dateline

I'm trying to delineate all river basins on a global 1/16 degree grid. The algorithm that the Basin tool in the Spatial Analyst Toolbox works well (fast) except it doesn't know how to handle the ...
5
votes
1answer
4k views

How to compute average slope and area-weighted average slope?

I am learning GIS for use in hydrologic analysis. Related to computation of overland flow there are two types of slope that I would like to be able to obtain from GIS. The first is average slope for ...
5
votes
1answer
2k views

Extracting flow accumulation to stream shapefile

I would like to create a shapefile that displays the flow accumulation for a given point in a stream channel. Is this possible? My client wants a map that shows the accumulated flow/catchment area ...
5
votes
1answer
1k views

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 ...
5
votes
3answers
3k views

How to calculate runoff in Rainfall Analysis?

I have 30 years daily rainfall data. How can i calculate the mean monthly runoff, minimum monthly runoff and maximum monthly runoff with the available rainfall data using GIS? I would like to use ...
4
votes
4answers
1k views

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 ...
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 ...
4
votes
1answer
5k views

Water Flow Analysis in ArcGIS Desktop?

If I know that 10,000+ gallons of water were going to be dropped at a single point how could I model where it would flow. I would prefer something that worked in ArcGIS and could create a layer.
4
votes
1answer
338 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
1k views

Mapping latlng values to a point on a HRAP grid

I have a copy of some NWS rainfall data loaded into a PostGIS database. Given a lat lng point, I want to find the rainfall for that given day. The original data are in XMRG format and projected in ...
4
votes
1answer
2k views

Determining direction of rivers i.e. which villages lie upstream and downstream?

I want to determine which villages lie upstream and which villages lie downstream big cities built on the side of rivers in Indonesia. I have the .shp file of villages and cities, the .shp file of all ...
4
votes
2answers
847 views

Generate Height Above the Nearest Drainage (HAND) using QGIS

I have a DEM I want to generate a HAND for and want to do so in QGIS. Does anyone know of any plugins or the processing steps to be able to do this?
4
votes
1answer
143 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 ...
4
votes
1answer
847 views

Horton Stream Ordering in ArcGIS?

Is there a way to order streams using the Horton (opposed to Horton-Strahler) method in ArcGIS (10.2.2)? I know the Stream Order tool allows you to use Strahler and Shreve.
4
votes
1answer
146 views

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 ...