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Split Catchment with PyGeoAPI

from __future__ import annotations

import geopandas as gpd
import shapely.geometry as sgeom

import pynhd

PyGeoAPI service provides four functionalities:

1. flow_trace: Trace flow from a starting point to up/downstream direction.

2. split_catchment: Split the local catchment of a point of interest at the point’s location.

3. elevation_profile: Extract elevation profile along a LineString.

4. endpoints_profile: Extract elevation profile along a path between two points.

5. cross_section: Extract cross-section at a point of interest along a flow line.

The pygeoapi function in PyNHD requires two inputs, a geopandas.GeoDataFrame that must contain all the required inputs corresponding to target services. Let’s take a look at them in an example:

gdf = gpd.GeoDataFrame(
    {
        "direction": [
            "none",
        ]
    },
    geometry=[sgeom.Point((1774209.63, 856381.68))],
    crs="ESRI:102003",
)
trace = pynhd.pygeoapi(gdf, "flow_trace")

In the split_catchment service we can set upstream to True to get the entire upstream catchments not just the split local catchments.

gdf = gpd.GeoDataFrame(
    {
        "upstream": [
            False,
        ]
    },
    geometry=[sgeom.Point((-73.82705, 43.29139))],
    crs=4326,
)
split = pynhd.pygeoapi(gdf, "split_catchment")

ax = split.plot(figsize=(8, 8), facecolor="lightgrey", edgecolor="black", alpha=0.8)
trace.plot(ax=ax, color="b", linewidth=3.0)
ax.axis("off")
ax.set_title("Split Catchment")
ax.margins(x=0)
ax.figure.set_dpi(100)
ax.figure.savefig("_static/split_catchment.png", bbox_inches="tight", facecolor="w", dpi=100)

The elevation_profile service returns the elevation profile along a LineString at a given number of points and a specified resolution for DEM.

coords = [
    [-108.45263, 38.97755],
    [-108.4535, 38.978],
    [-108.454393, 38.977915],
    [-108.45495, 38.97837],
]
gdf = gpd.GeoDataFrame(
    {
        "numpts": [
            101,
        ],
        "dem_res": [
            1,
        ],
    },
    geometry=[sgeom.LineString(coords)],
    crs=4326,
)
profile = pynhd.pygeoapi(gdf, "elevation_profile")

ax = profile.plot(
    column="elevation",
    legend=True,
    figsize=(6, 6),
    legend_kwds={"label": "Elevation (m)", "orientation": "horizontal", "shrink": 0.4},
)
ax.set_title("Elevation profile along a line")
ax.set_axis_off()