Quickstart

The most common workflow to derive flow direction from digital elevation data and subsequent delineate basins or vectorize a stream network can be done in just a few lines of code.

To read elevation data from a geotiff raster file elevation.tif do:

import rasterio
with rasterio.open("elevation.tif", "r") as src:
    elevtn = src.read(1)
    nodata = src.nodata
    transform = src.transform
    crs = src.crs

Derive a FlwdirRaster object from this data:

import pyflwdir
flw = pyflwdir.from_dem(
    data=elevtn,
    nodata=src.nodata,
    transform=transform,
    latlon=crs.is_geographic,
)

Delineate basins and retrieve a raster with unique IDs per basin: Tip: This raster can directly be written to geotiff and/or vectorized to save as vector file with rasterio

basins = flw.basins()

Vectorize the stream network and save to a geojson file:

import geopandas as gpd
feat = flw.streams()
gdf = gpd.GeoDataFrame.from_features(feats, crs=crs)
gdf.to_file('streams.geojson', driver='GeoJSON')