NCAmapper: A GIS Model for Accurate Quantification of the Spatiotemporal Changes in Non-Contributing Areas and Depressional Storage

This repository contains the NCAmapper software source code and the model inputs and results for the three tested watersheds: the Smith Creek Research Basin (SCRB), the Souris River Basin (SRB), and the Milk River Basin (MRB). The software and data are part of the following paper "NCAmapper: A GIS Model for Accurate Quantification of the Spatiotemporal Changes in Non-Contributing Areas and Depressional Storage" submitted to the Journal of Hydrology for publication.

Check the GitHub repository for the most up-to-date version of the NCAmapper model.

The following folders are included:

• 1-NCAmapper_script.zip: This zipped folder contains the NCAmapper script/model.
  •  main_NCAmapper.R: the main file to run the NCAmapper model. It needs the input directory (inp_dir), which is the working directory that contains the inputs and it is the same directory where outputs will be written.
  • functions_NCAmapper.R: a script that contains the used functions/modules by NCAmapper.

• The three other zipped files contain the input data and results of the three test basins. The following folder structure applies to any of the test basins, but an example from the Smith Creek Research Basin (SCRB; 2-Smith_Creek_basin.zip) is provided below:
  • comparison: a directory containing rasters that compare the output of NCAmapper to benchmark datasets, which include the following files:
    • PFRA_vs_NCAmapper_SCRB_2yrs.tif: a raster file that shows the agreement between the PFRA map and the NCAmapper NCA map for a 2-year event (Figure 4 in the paper).
    • PRIMA_minus_NCAmapper_depth_100yr.tif: a raster file that shows the difference in the depth field between PRIMA and NCAmapper spatial depressional storage depth for a 100-year event (Figure 5 in the paper). Note that this file only exists for the SCRB as it is the only basin that PRIMA simulated.
    • PRIMA_vs_NCAmapper_extents_100yr.tif: a raster file that shows the agreement between PRIMA and NCAmapper in terms of simulating spatial water extents for a 100-year event (Figure 5 in the paper). Note that this file only exists for the SCRB as it is the only basin that PRIMA simulated.
  • NCAmapper_output: a directory that contains the final outputs of the NCAmapper model, which are used to map the NCAs and pothole water extents. This directory includes the following files:
    • CA_n_xyr_d_mm.tif: contributing area (CA) of the basin for "n" time step, which corresponds to an "x" return period (years) with a precipitation depth of "d" in mm.
    • depr_stor_dep_n_xyr_d_mm.tif: spatial depth field for the different depressions for a specific return period. The file follows the same name coding as the CA file.
    • depression_state.csv: a csv file containing the state (pond volume) for each depression for all return periods. The first two columns show the depression number and volume, while any subsequent column shows the pond volume (state) for that depression for a specific time step (return period).
    • depressions_summary.csv: a csv file containing relevant information about the depressions in the basin (number, area, volume, depth, basin area, cascading order, etc.). This file (table) is the output of the second module "depressions summary" of the NCAmapper. Each column represents a depression property (self-describing column header) and each row shows that information for a specific depression.
    • map_n.jpeg: a figure that shows the spatial NCA and water depth/extents for time step n.
    • NCA_n_xyr_d_mm.tif: a raster file that shows the NCAs within the basin for different return periods. The file follows the same name coding as the CA file.
  • NCAmapper_temp: a directory that contains temporary (diagnostic) outputs used by NCAmapper, which includes the following files:
  • • D8_flow_pointer_filled.tif: flow direction raster.
    • depression_depth_non_zeros.tif: a raster file with depressions depth after filtering out (excluding) depressions that meet the user-defined depth and area thresholds.
    • depression_depth.tif: a raster file with depressions depth for all depressions identified from the DEM
    • depression_no_non_zeros.tif: a raster file with depressions number after filtering out (excluding) depressions that meet the user-defined depth and area thresholds.
    • depression_no_rvr.tif: a raster file with depressions that are located in the main river and meet the area threshold criterion.
    • depression_no.tif: a raster file with depression number for all depressions identified from the DEM.
    • depression_watershed.tif: depression basin for the final depressions (depression_no_non_zeros.tif)
    • filled_dem.tif: filled dem raster.
    • flow_acc_fill.tif: flow accumulation raster.
    • nonfill_depressions_n_xyr_d_mm.tif: a raster file that contains the non-filled depressions for a specific return period. The file follows the same name coding as the CA file.
    • watershed_n_xyr_d_mm.tif: watershed raster file for the non-filled depression for different return periods. Used to estimate NCAs.
    • wl_n_xyr_d_mm.tif: water elevation inside the depressions for different return periods. This file is used to estimate the depr_stor_dep_n_xyr_d_mm.tif raster file.
  • NCAmapper_config.ini: main input file to the NCAmapper model to configure the run, where users can specify input files' names and user-defined threshold. Each line has a clear description at its end.
  • SCRB_boundary.*: basin boundary in ESRI shapefile format.
  • SCRB_COP30mDEM_UTMz13.tif: input raster Copernicus 30m DEM in projected coordinate system.
  • SCRB_obs_rivers.*: observed rivers centerline in ESRI shapefile format.
  • SCRB_PFRA_map.*: the benchmark PFRA NCA map in ESRI shapefile format.
  • SCRB_RP_rain_depth.csv: the different return periods (in years; first column) and the corresponding precipitation depth (second column) in mm.

Note: to run NCAmapper, the user must use projected and uncompressed DEM and input shapefiles.

Abstract:

The North American prairie region is characterized by numerous land depressions causing variable non-contributing areas (NCAs) that impact runoff translation into streamflow. Current hydrological models address temporal changes in NCA but neglect spatial distribution and geolocation. The only NCA maps available for the prairies were derived by the Prairie Farm and Rehabilitation Association (PFRA) from paper-based contour maps using subjective interpretation of a 2-year rainfall event. PFRA maps are therefore static and inadequately represent the dynamic nature of NCAs across different return periods. This study introduces NCAmapper, a GIS-based model relying on digital elevation models (DEMs) to map NCAs dynamically for different runoff events in prairie and arctic regions. Evaluation of NCAmapper demonstrates its capabilities in dynamically representing the spatiotemporal variability in NCAs corresponding to different rainfall events. NCAmapper additionally enhances hydrological model parameterization, aiding practitioners in quantifying effective drainage areas and evaluation of flood vulnerability.