I have delineated a river centreline and interpolated the Z values from a DEM (SRTM 90m) to generate a 3D polyline that represents the river centreline. I have then adjusted the Z values within the 3D river centreline and increased it by 20m and 40m respectively. I've tried to use Visibility Analysis tool to try to generate the floodplain, but the results aren't great even after adjusting the vertical, horizontal and radius parameters. Any alternative would appreciated.
So as explained, I'm trying to delineate the expected inundated surface areas coarsely from the river centreline, based on an adjusted Z value, then trying to determine the horizontal impact area of the DEM that is covered by water.
Regards
I came across a nice post where William Huber (Esri forum senior member and MVP) wrote about simulating a flood:http://www.quantdec.com/SYSEN597/studies/flood/index.htmIt's an interesting article and I recommend you to read it. He also included an avenue script to calculate the change in flood plains over time. I translated this into a small python script (10.x) and it seems to works. William uses for his demo area (relatively flat) the following settings:nSourceElevation = 200
nFloodMax = 205
nIncrement = 0.25
nExtent = 200
In my case I used a more mountainous area, so the values area different. Investigate your data to see what setting fit your needs.This is what resulted, before:[ATTACH=CONFIG]29100[/ATTACH]and after:[ATTACH=CONFIG]29101[/ATTACH]#-------------------------------------------------------------------------------
# Name: SimulateFlood.py
# Purpose: Simulate a Flood
#
# Source: William A. Huber (Quantitive Decisions)
# http://www.quantdec.com/SYSEN597/studies/flood/index.htm
#
# Created: 14-11-2013
#-------------------------------------------------------------------------------
def main():
import arcpy,os
arcpy.CheckOutExtension("Spatial")
arcpy.env.workspace = r'C:\Project\_Forums\Flooding\fgdb\testflooding.gdb'
source = r'C:\Project\_Forums\Flooding\fgdb\testflooding.gdb\source' # The source water body (raster)
dem = r'C:\Project\_Forums\cost\fgdb\test.gdb\elevutm16n' # The elevation DEM (raster)
floodname = r'C:\Project\_Forums\Flooding\fgdb\testflooding.gdb\Flood_' # outputs
# settings
nSourceElevation = 100 # The elevation corresponding to the source body
nFloodMax = 400 # The maximum flood elevation; must not be less then nSourceElevation
nIncrement = 20 # The flooding elevation increment
nExtent = 750 # Do not flood outwards more than this many cells.
nTiny = 0.9/nExtent # Used for limiting flood extents
sourceRas = arcpy.Raster(source)
demRas = arcpy.Raster(dem)
steps = int((nFloodMax - nSourceElevation) / nIncrement) + 1
for i in range(0,steps):
xElevation = (i * nIncrement) + nSourceElevation
outname = "{0}{1}".format(floodname,i)
cost = (demRas > xElevation)+nTiny
costdist = arcpy.sa.CostDistance(sourceRas, cost, "#", "#")
flood = costdist <= (nExtent*nTiny)
if arcpy.Exists(outname):
arcpy.Delete_management(outname)
flood.save(outname)
sourceRas = arcpy.sa.Log10(outname) # Converts 1 to 0, 0 to NoData
del cost, costdist, flood
print "ready..."
if __name__ == '__main__':
main()Kind regards,Xander
