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7

You didn't specify a software requirement for your solution (although there is an ArcGIS tag on the question) so I've provided a method below based on the free and open-source GIS Whitebox Geospatial Analysis Tools, for which I am a developer. Whitebox GAT has a tool called Elevation Above Stream (see image below): For a given DEM and rasterized stream ...


5

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


4

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 steps, but if it exists it's most likely to be in ArcHydro (never heard of Government toolbox though). However, this is quite a simple process involving only three ...


4

R. 70 and 80 will be difficult, Weather/ Preciptation data only: There first address for preciptation data is European Centre for Medium-Range Weather Forecasts in Reading. http://www.ecmwf.int/ There are bunch of data products mostly free for download. Look for the data center, reanalysis projects adressing the 60s and 80s. There is a project called ...


4

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 to be rasterized to be a Seeds raster beforehand. Please make sure the dimension (cell size, extent) of the Seeds raster is the same as your DEM. Lake Flood ...


4

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 flood are negative. Now add 2 meters to this new raster, and then extract all pixels with positive values. This should become the new flood limits. (Caveat: ...


3

Did you check GRASS r.lake function: https://grass.osgeo.org/grass70/manuals/r.lake.html


3

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 Intersection tool may be of interest to you. You can input two polygons (flood zone and population block groups, for example) and tabulate what percentage of ...


3

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 intertidal zone (somewhere between MHHW and MLLW), so depending on the DEM data, tidal conditions during the survey could be showing. Coastal flood modelling ...


3

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 available there also.


3

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 different land cover types complicate the equation and therefore the flood extent. The folks associated with the National Water Model have been working towards this ...


3

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", vertices_only="DENSIFY", pyramid_level_resolution="0") arcpy.SplitLine_management(in_features="streams3d", out_feature_class="C:/SCRATCH/bits3d.shp") arcpy....


2

When you start getting into hydrograph routing (flow rate vs time), you are leaving the GIS realm and get into specialized hydraulic modeling software. HEC-RAS is great for open channels, and can handle pipe flow, but needs hydrology (how much runoff are you getting) input (often from HEC-HMS). The mix of hydrologic and hydraulic modeling required to (...


2

I recommend you try the Surface Difference tool in 3D Analyst. The datasets you described are what is used as input for this tool as shown in the Help topic, Floodplain delineation from Lidar points. Lidar is used to create the dem used in the tool but you already have that so can ignore that part.


2

I've never done flood modeling before but one simple approach I could think of is Interpolate the point data height of water values to generate a height of water raster Subtract the elevation model height from the water height raster to determine which areas would be under water


2

ASTER and MODIS both have global coverage and are suited for larger scale flood analysis. ASTER has a temporal resolution of 16 days and contains 14 spectral bands in VNIR (15m), SWIR (30m) and TIR (90m). Note that ASTER SWIR data acquired from late April 2008 to the present exhibit anomalous saturation of values and anomalous striping. MODIS has a higher ...


2

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 compute the flooded volume above each pixel and return the sum of these volumes. This is (roughly) the total flooded volume at that elevation. If the volume is ...


2

To do this you would need a 3d Analyst and Spatial Analyst license. First, elevate your waterbody using Interpolate Shape, this will give the baseline for your elevations by attributing the polygon with the Z values from the DEM to each vertex. Build a terrain with your waterbodies as the elevation data source (perhaps buffer by a small amount and include ...


2

A robust but programmatic solution would be something along these lines (roughly, Pythonic pseudocode): # D is the DEM, W is the true/false water body mask # delta is the max height difference for flood-prone areas F = D * W # F is the DEM with dry land masked out (starting flood positions) while True: changed = False for c in F: # for every cell ...


2

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 else a value of 0. The parameters are pretty self explanatory for the Reclassify tool. Con, on the other hand, is a bit more cryptic. Here is an example of the ...


2

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 elements outside this area, if the precision there is less critical. In Flo-2D, you might also want to check the water depth and increase the roughness if the ...


2

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.


2

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 polygons over those to display. In addition, you could look into Esri's Floodplain delineation from lidar points, provides a general overview of options of using ...


2

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 "impact" areas using either Eucledian Allocation or Watersheds of the bits: Transfer increased levels from the bits to relevant polygons and compute new flood ...


2

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. If you want the maximum water extent in a certain area, just use max extent instead occurrence layer.


2

The short answer is Yes, but creating and editing a TIN surface is beyond the scope of this forum, you need to be training yourself if you are asking such questions. As you have tagged this as an ArcMap question I suggest you head over to esri training and complete the Creating 3D Data using ArcGIS course.


2

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 surface, do a quick raster calc to find areas where terrain is higher than the water surface and youll get an approximate extent of flooding. The more standard ...


1

It's possible using IDW in 3d Analyst or Spatial Analyst. This can create a Raster with elevation by interpolating between the points. It's important to make sure the buffer is large enough and parameters for the interpolation is correct (depends on what you need). Then using Raster Calculator (DEM - WaterLevel from IDW) and everything positive will be ...


1

A partial answer to my question was found here: Flood Elevation Setback. Partial due to preferring an arc based solution. I was able to create the following, using a flow accumulation grid for streams and a flow direction grid, all derived from a DEM. May play around with parameters a bit.


1

Although I have done a lot with rivers I would not consider myself a flood modeller and I suspect I have over simplified my answer. There is the Expand tool that you could use to expand out the expansion of a lake 1 pixel at a time which you could then test to see if is below 1m or not. If it is, you keep it and then feed back the expanded lake? So this ...


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