5
votes
Generate flood map using qgis
This is a good video that provides you with a walkthrough on generating a flood inundation map, QGIS Flood Risk Mapping Walkthrough. Also, you can find additional case study here
- 12k
4
votes
Accepted
Calculating Flooded area / Inundation in ArcGIS for Desktop?
Your workflow should get you what you need.
I'd recommend to use Con for the first two steps (then you can aggregate them into only one step).
I don't know of any existing tool that does these ...
- 4,928
4
votes
Showing overland flow route on DEM in QGIS?
It is called Lake Flood.
I recommend SAGA GUI, but if it has to be done in QGIS, you can find it in the Processing Toolbox | SAGA | Terrain Analysis - Hydrology | Lake flood.
Your manhole points has ...
- 30.4k
4
votes
Offset raster boundary by elevation
How about this:
If you subtract the original DEM from the flood elevation raster, you will get water depth. All areas with positive values are flooded (positive water depth) and all areas outside the ...
- 15.4k
3
votes
Multi-Spectral High Resolution Satellite images for flood events
You may consider using Google Earth Engine: filter desired imagery by date (pre-post flood) and location (polygons of approximate locations). Machine learning algorithms like random forest is readily ...
- 151
3
votes
DEM showing areas in the ocean to be greater than 0m (my MSL in my project)
The ocean is a dynamic environment, depending on conditions (thermal expansion, swell heights, bathymetric profile, location, etc.) this can be normal. Additionally, MSL is really in the area of the ...
- 31
3
votes
How to design a flood with water elevation on a specific point?
Did you check GRASS r.lake function:
https://grass.osgeo.org/grass70/manuals/r.lake.html
- 2,183
3
votes
Accepted
Estimating population in flood zones?
Population is an estimate, as it stands, so I'm assuming you are looking for a 'best-guess' type of workflow that will give the best results for the littlest amount of time spent.
ArcGIS's Tabulate ...
- 3,686
3
votes
Determining flood extents based on a daily flow?
This quickly becomes a very complicated problem if you're trying to compute true flood extents. You can estimate flow through an open channel using Manning's Equation, but flow velocities over ...
- 979
3
votes
Creating contours based on polyline using ArcMap?
These workflow:
arcpy.InterpolateShape_3d(in_surface="dem", in_feature_class="STREAMS", out_feature_class="C:/SCRATCH/streams3d.shp", sample_distance="", z_factor="1", method="BILINEAR", ...
- 22.5k
3
votes
Delete geometries based on intersection with another layer
You can use the processing tool "Extract by location" to extract the buildings that are disjoint from the flood plains:
- 67.1k
2
votes
Extracting features from raster data using ArcGIS Desktop?
You can use Reclassify (Spatial Analyst) or Con (Spatial Analyst) to perform this type of image thresholding. In your case, it is common to assign pixel values of interest a value of 1 and everything ...
- 51.4k
2
votes
Simplified flood "model" / estimation from elevation data
I can think of a very simple iterative solution.
Given a DEM and a 'seed' point, use the flood fill algorithm to fill pixels below an arbitrarily selected start elevation. Modify the algorithm to ...
- 3,101
2
votes
HEC-RAS limitation on cross sections?
You only need to input a manning's n value where there is a change. For example the picture below shows a cross section using three manning's n values, but well over three coordinate points.
- 434
2
votes
Solving computing time problem when grid size element increases in flood model?
Depending on your problem and the nature of the details you want to keep, you might want to :
Use a channel with cross sections in Flo-2D to have a close approach of the river bed
Use coarser ...
- 1,917
2
votes
Accepted
Maximum water extent JRC dataset
Yes, 'max_extent' is not defined in your scope. Check your code, there isn't any object called max_extent
Map.addLayer(gsw.select('max_extent'))
Is unclear the aim of your analysis, please be clear. ...
- 13.1k
2
votes
Increasing Flood Plain
Workflow I am using:
Split flood outline by points placed at regular interval:
Interpolate bits into 3D polylines, using elevation model and compute average elevation (Z) values for them.
Identify "...
- 22.5k
2
votes
Increasing Flood Plain
You could create 1' contour lines, using your LiDAR data. Then use those contour lines to calculate your 1', 2', 5' increase. Using a basic approach in determining the increase potential and create ...
- 12k
2
votes
Editing TIN surface by polygon using ArcMap
The short answer is Yes, but creating and editing a TIN surface is beyond the scope of this site, you need to be training yourself if you are asking such questions. As you have tagged this as an ...
- 42.6k
2
votes
How to find out which areas are affected by flooding due to heavy rain?
I am unsure how accurate you want your results to be, my understanding is that you can do one of two approaches:
Find known water level points for the rainfall event and create an interpolated ...
- 832
2
votes
Accepted
Calculating area in QGIS, defined as zone with relative elevation compared to a river
This solution provides a workflow to do exactly what you asked for. The workflow might not be the standard way how to calculate flooded areas, but since you asked for it, here is a way how to do it ...
- 63.1k
2
votes
Delete geometries based on intersection with another layer
Use select by location tools on QGIS HERE Vector->Research tools->Select by Location
to know more :
https://docs.qgis.org/3.16/fr/docs/user_manual/processing_algs/qgis/vectoroverlay.html?...
- 436
1
vote
Issue with FEMA OGC Web Feature Service returning HTTP 400 error when attempting to download GML file
You can determine the number of results by using resultType=hits& like:
https://hazards.fema.gov/gis/nfhl/services/public/NFHL/MapServer/WFSServer?SERVICE=WFS&VERSION=1.1.0&REQUEST=...
- 13.2k
1
vote
Issue with FEMA OGC Web Feature Service returning HTTP 400 error when attempting to download GML file
It seems that this service struggles with large(ish) requests. If you change your second request to maxFeatures=10 it returns correctly so there is no issue with the bounds or the request, it is just ...
- 79.9k
1
vote
Converting a point file, into a smoother set?
if you already have a point vector layer, you can extract the information from your DEM to your point layer using the Spatial Analyst tool Extract to Point. You can use Spatial Join to join your ...
- 745
1
vote
Finding Vector data that is in the area of a specific value of Raster data
There a several ways to solve this problem. One is to reclassify the raster so that any area less than 5 meters gets a value of 1 and everything above 5 meters gets a value of NoData. Convert the ...
- 9,207
1
vote
Converting polyline to polygon in ArcGIS Desktop for floodplain map?
As commented by @mkennedy:
There's also Feature to Polygon tool, but you have to have an advanced license.
The Feature to Polygon tool:
Creates a feature class containing polygons generated ...
- 64.9k
1
vote
What Algorithms to use for Levee breach Analysis?
Hydraulic models can tell a lot of different things. 1D, 2D and 3D models can tell different information. Apparently 3D models will give velocities and depth. The speed of breach also can be ...
- 3,069
1
vote
Explanation of HAND (height above nearest drainage) model procedure
I will assume you have your DEM, have been able to calculate the flow direction raster (the ArcGis help has a good explanation). You also need to have defined a raster of the drainage which has values ...
- 293
1
vote
Flood Plain Mapping using HEC-GeoRAS and ArcMap?
Inundation mapping at junctions isn't perfect within HEC-RAS. I'd suggest manually editing the output based on your judgement.
- 434
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