Flood Grid Rescaler

QGIS Processing scripts for rescaling or changing the resolution of flood hazard rasters.

Tested against QGIS 3.34.5

UPDATES

• 2024 05 17: added Water Grid from Complement tool to easily convert between WSE and WSH grids
• 2024 01 19: added pixel based isolated filter for the Resolution Enhancer tool

01 Description

Includes the following tools:

• Resolution Enhancer (WSE): Three methods for interpolating a high resolution WSE grid using a high resolution DEM and simple hydraulic assumptions described in Bryant et. al., (2024). For more advanced applications and features, see the FloodDownscaler2 project. Requires WhiteboxTools for QGIS plugin.
• Aggregation via Averaging: Two methods for coarsening flood hazard grids described in Bryant et. al., (2023)
• Water Grid from Complement: Two tools to generate a Water Surface Elevation (WSE) or Water Surface Height (WSH) grid from its complement and a DEM.

02 Installation Instructions

download the scripts

Download the floodrescaler.zip archive from the latest release then unzip to your local machine.

Alternatively, download the processing scripts of interest from the processing folder source code directly.

add to your QGIS profile

In the QGIS Processing Toolbox, select the python icon drop down , and Add Script to Toolbox.... This should load new algorithms to the Scripts/FloodRescaling group on the Processing Toolbox as shown below:

Alternatively, add the unzipped folder as a Scripts folder to your QGIS profile: Settings > Processing > Scripts > Scripts folders

install and configure WhiteboxTools

Ensure the WhiteboxTools for QGIS plugin is installed and configured. Note this is only required for the Downscaling/CostGrow algo. Tested against v2.2.0.

03 Use

Instructions are provided on the algorithm dialog

04 Example Data

Example data is provided in the examples folder

05 Attribution

If you use these tools for your work, please cite the following:

Aggregation via Averaging

@article{bryant_bias_2023,
	title = {Bias in {Flood} {Hazard} {Grid} {Aggregation}},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2023WR035100},
	doi = {10.1029/2023WR035100}, 
	journal = {Water Resources Research},
	author = {Bryant, Seth and Kreibich, Heidi and Merz, Bruno},
	year = {2023},
}

Resolution Enhancement

@Article{hess-28-575-2024,
	AUTHOR = {Bryant, S. and Schumann, G. and Apel, H. and Kreibich, H. and Merz, B.},
	TITLE = {Technical Note: Resolution enhancement of flood inundation grids},
	JOURNAL = {Hydrology and Earth System Sciences},
	VOLUME = {28},
	YEAR = {2024},
	NUMBER = {3},
	PAGES = {575--588},
	URL = {https://hess.copernicus.org/articles/28/575/2024/},
	DOI = {10.5194/hess-28-575-2024}
}


@inproceedings{lindsay_whitebox_2014,
	title = {The whitebox geospatial analysis tools project and open-access {GIS}},
	url = {https://jblindsay.github.io/ghrg/pubs/LindsayGISRUK2014.pdf},
	urldate = {2022-04-11},
	booktitle = {Proceedings of the {GIS} {Research} {UK} 22nd {Annual} {Conference}, {The} {University} of {Glasgow}},
	author = {Lindsay, JB},
	year = {2014},
	pages = {16--18},
}

06 Development

• create a virtual environment from the supported QGIS version and the ./requirements.txt file.
• add a ./definitions.py file similar to the below
• add the QGIS python plugins directory (C:\Users\cef\AppData\Local\QGIS\QGIS3\profiles\dev\python\plugins) to your PYTHONPATH. Needed by the downscaler to mimic the dependency on WBT.

definitions.py

import pathlib, os
src_dir = os.path.dirname(os.path.abspath(__file__))

wrk_dir = os.path.expanduser('~')

#add your WhiteBoxTools executable file
wbt_exe = r'l:\06_SOFT\whitebox\v2.2.0\whitebox_tools.exe'