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GEE Code
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sagycohen committed Aug 23, 2022
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/* ------------------------------------------------------------------------------------
FwDET-GEE-v2 is an update and improvement to FwDET-GEE (Peter et al. 2020a; Peter et al.
2020b). FwDET was conceptualized by Sagy Cohen (University of Alabama, Department of
Geography) and prepared for use in ArcGIS (Cohen et al. 2019). FwDET-GEE was adapted for
use in Google Earth Engine by Brad G. Peter (University of Arkansas, Department of
Geosciences).

Cohen, S., Raney, A., Munasinghe, D., Loftis, J.D., Molthan, A., Bell, J., Rogers, L.,
Galantowicz, J., Brakenridge, G.R., Kettner, A.J. and Huang, Y.F., 2019. The Floodwater
Depth Estimation Tool (FwDET v2. 0) for improved remote sensing analysis of coastal
flooding. Natural Hazards and Earth System Sciences, 19(9), pp.2053-2065.

Peter, B.G., Cohen, S., Lucey, R., Munasinghe, D., Raney, A. and Brakenridge, G.R., 2020b.
Google Earth Engine Implementation of the Floodwater Depth Estimation Tool (FwDET-GEE)
for rapid and large scale flood analysis. IEEE Geoscience and Remote Sensing Letters.

Peter, Brad; Cohen, Sagy; Lucey, Ronan; Munasinghe, Dinuke; Raney, Austin, 2020a,
"A Google Earth Engine implementation of the Floodwater Depth Estimation Tool
(FwDET-GEE)", https://doi.org/10.7910/DVN/JQ4BCN, Harvard Dataverse, V5.
-------------------------------------------------------------------------------------*/

// Input ------------------------------------------------------------------------------

// Flood extent layer (must be a raster image)
var floodLayer = ee.Image('users/cartoscience/FwDET-GEE-v2/FID01_USGSFIM_LA_BatonRouge')

var demSource = 'NED' // See parameterization options in the following section
var testNumber = 'T31' // See parameterization options in the following section
// or specify custom test parameters below (customTest)

// [slope filter, slope filter option ('TRUE' or 'FALSE'),
// number of iterations, iterations option ('TRUE' or 'FALSE')]
var customTest = [0.5,'TRUE',10,'TRUE']
var customSelect = 'TRUE' // set to 'TRUE' to run custom parameters
// 'FALSE' will use parameter set above (testNumber)

// Export options
var fileSuffix = '08222022'
var exportFolder = 'GEE_export'

// FwDET-GEE-v2 •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••

// Parameters -------------------------------------------------------------------------
var demOptions = {
'NED': ['USGS/NED','elevation'],
'NASADEM': ['NASA/NASADEM_HGT/001','elevation'],
'ALOS': ['JAXA/ALOS/AW3D30/V2_2','AVE_DSM'],
'SRTM30': ['USGS/SRTMGL1_003','elevation'],
'SRTM90': ['CGIAR/SRTM90_V4','elevation'],
'WWF': ['WWF/HydroSHEDS/03VFDEM','b1'],
'MERIT': ['MERIT/DEM/v1_0_3','dem'],
'ASTER': ['NASA/ASTER_GED/AG100_003','elevation']
}

// [slope filter, slope filter option ('TRUE' or 'FALSE'),
// number of iterations, iterations option ('TRUE' or 'FALSE')]
var testParams = {
'T01': [0.5,'TRUE',1,'TRUE'],
'T02': [0.5,'TRUE',2,'TRUE'],
'T03': [0.5,'TRUE',3,'TRUE'],
'T04': [0.5,'TRUE',4,'TRUE'],
'T05': [0.5,'TRUE',5,'TRUE'],
'T06': [1,'TRUE',1,'TRUE'],
'T07': [1,'TRUE',2,'TRUE'],
'T08': [1,'TRUE',3,'TRUE'],
'T09': [1,'TRUE',4,'TRUE'],
'T10': [1,'TRUE',5,'TRUE'],
'T11': [1.5,'TRUE',1,'TRUE'],
'T12': [1.5,'TRUE',2,'TRUE'],
'T13': [1.5,'TRUE',3,'TRUE'],
'T14': [1.5,'TRUE',4,'TRUE'],
'T15': [1.5,'TRUE',5,'TRUE'],
'T16': [2,'TRUE',1,'TRUE'],
'T17': [2,'TRUE',2,'TRUE'],
'T18': [2,'TRUE',3,'TRUE'],
'T19': [2,'TRUE',4,'TRUE'],
'T20': [2,'TRUE',5,'TRUE'],
'T21': [2.5,'TRUE',1,'TRUE'],
'T22': [2.5,'TRUE',2,'TRUE'],
'T23': [2.5,'TRUE',3,'TRUE'],
'T24': [2.5,'TRUE',4,'TRUE'],
'T25': [2.5,'TRUE',5,'TRUE'],
'T26': ['x','FALSE',1,'TRUE'],
'T27': ['x','FALSE',2,'TRUE'],
'T28': ['x','FALSE',3,'TRUE'],
'T29': ['x','FALSE',4,'TRUE'],
'T30': ['x','FALSE',5,'TRUE'],
'T31': ['x','FALSE','x','FALSE']
}

// Preprocessing •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••

// Retrieving parameters ---------------------------------------------------------------
var test = testParams[testNumber]
if (customSelect == 'TRUE') {
test = customTest
}
var filterBounds = test[3]
var iterations = test[2]
var filterSlope = test[1]
var slopeThreshold = test[0]
var filterKernel = 5

// Layer and DEM extraction ------------------------------------------------------------
var layerMask = floodLayer.gt(0)
var layerPrj = floodLayer.projection().nominalScale()
var aoi = floodLayer.geometry().bounds().buffer(1000).bounds()
var demFields = demOptions[demSource]
var dem = ee.Image(demFields[0]).select(demFields[1]).clip(aoi)
var prj = dem.projection()
var res = prj.nominalScale()

// Flood modification ------------------------------------------------------------------
var flood = floodLayer.reproject(prj).rename('flood')
var floodMask = flood.mask().not()
var floodExtent = floodMask.updateMask(floodMask.eq(0))
var expand = floodExtent.focal_max(res,'square','meters')
var mask = expand.mask().add(floodExtent.mask())
var demEdge = dem.updateMask(mask.eq(1))
var demE = demEdge

// Slope and focal statistics filter ---------------------------------------------------
if (filterSlope == 'TRUE') {
var slopeMask = ee.Terrain.slope(dem).gt(slopeThreshold)
demEdge = demEdge.updateMask(slopeMask.eq(0))
}

var edgeMod = demEdge
if (filterBounds == 'TRUE') {
for (var i = 0; i < iterations; i++) {
edgeMod = edgeMod.focal_mean(res.multiply(filterKernel),'square','meters')
}
dem = dem.where(demE,edgeMod)
}

// FwDET-GEE-v2 ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••

// Cumulative cost interpolation -------------------------------------------------------
var mod = dem.updateMask(floodExtent.mask().eq(0))
var source = mod.mask()
var val = 10000
var push = 5000
var cost0 = ee.Image(val).where(source,0).cumulativeCost(source,push)
var cost1 = ee.Image(val).where(source,1).cumulativeCost(source,push)
var cost2 = mod.unmask(val).cumulativeCost(source,push)
var costFill = cost2.subtract(cost0).divide(cost1.subtract(cost0))
var costSurface = mod.unmask(0).add(costFill)
var costDepth = costSurface.subtract(dem)

costDepth = costDepth.convolve(
ee.Kernel.square({
radius: res.multiply(3),
units: 'meters',
normalize: true
})
)


// FwDET-GEE-v2 cleaning and visualization ---------------------------------------------
var fwdet = costDepth.where(costDepth.lt(0),0).rename('FwDET-GEE-v2')
.updateMask(floodLayer)

var histFwDET = ui.Chart.image.histogram({
image: fwdet.updateMask(fwdet.neq(0)),
region: fwdet.geometry(),
scale: res,
maxPixels: 1e13
})

print(histFwDET)
Map.addLayer(layerMask.updateMask(layerMask.eq(1)), {palette:'red'}, 'inundation extent', false)
Map.addLayer(fwdet, {min: 0, max: 5, palette: ['white','blue','purple']}, 'fwdet')
Map.setOptions('HYBRID').centerObject(fwdet)

// FwDET-GEE-v2 layer export -----------------------------------------------------------
var naming = 'FwDET-GEE-v2_'+fileSuffix
Export.image.toDrive({
image: fwdet,
description: naming,
folder: exportFolder,
fileNamePrefix: naming,
region: fwdet.geometry(),
scale: res,
maxPixels: 1e13
})

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