arcgis.features.hydrology module

These functions help you use hydrology analysis.

trace_downstream

arcgis.features.hydrology.trace_downstream(input_points, point_id_field=None, source_database='Finest', generalize=False, gis=None, future=False)
../_images/trace_downstream.png

The trace_downstream method delineates the downstream path from a specified location. Esri-curated elevation data is used to create an output polyline delineating the flow path downstream from the specified input location. This method accesses a service using multiple source databases which are available for different geographic areas and at different spatial scales.

Argument

Description

input_points

Required FeatureSet or Spatially Enabled DataFrame Points delineating the starting location to calculate the downstream location from. See Feature Input.

point_id_field

Optional string. Field used to identify the feature from the source data. This is useful for relating the results back to the original source data.

source_database

Optional string. Keyword indicating the source data that will be used in the analysis. This keyword is an approximation of the spatial resolution of the digital elevation model used to build the foundation hydrologic database. Since many elevation sources are distributed with units of arc seconds, this keyword is an approximation in meters for easier understanding.

  • Finest: Finest resolution available at each location from all possible data sources.

  • 10m: The hydrologic source was built from 1/3 arc second - approximately 10 meter resolution, elevation data.

  • 30m: The hydrologic source was built from 1 arc second - approximately 30 meter resolution, elevation data.

  • 90m: The hydrologic source was built from 3 arc second - approximately 90 meter resolution, elevation data.

The default value is ‘Finest’.

generalize

Optional boolean. Determines if the output downstream trace lines will be smoothed into simpler lines.

The default value is False.

gis

Optional GIS Object instance. If not provided as input, a GIS object instance logged into an active portal with elevation helper services defined must already be created in the active Python session. A GIS object instance can also be optionally explicitly passed in through this parameter.

future

Optional boolean. If True, the result will be a GPJob and results will be returned asynchronously.

Returns

A new FeatureSet

# USAGE EXAMPLE: To trace downstream path from from the outlet points.
path = trace_downstream(input_points=fs,
                        source_database='Finest',
                        generalize=False)

watershed

arcgis.features.hydrology.watershed(input_points, point_id_field=None, snap_distance=10, snap_distance_units='Meters', source_database='Finest', generalize=False, gis=None, return_snapped_points=True, future=False)
../_images/create_watersheds.png

The watershed is used to identify catchment areas based on a particular location you provide and ArcGIS Online Elevation data.

Argument

Description

input_points

Required FeatureSet or Spatially Enabled DataFrame. Points delineating the starting location to calculate the downstream location from. See Feature Input.

point_id_field

Optional String. Field used to identify the feature from the source data. This is useful for relating the results back to the original source data.

snap_distance

Optional float. The maximum distance to move the location of an input point.

Interactive input points and documented gage locations may not exactly align with the stream location in the DEM. This parameter allows the task to move the point to a nearby location with the largest contributing area.

The snap distance should always be larger than the source data resolution. By default, the snapping distance is calculated as the resolution of the source data multiplied by 5.

The default value is 10.

snap_distance_units

Optional String. The linear units specified for the snap distance.

Choice list: [‘Meters’, ‘Kilometers’, ‘Feet’, ‘Yards’, ‘Miles’].

The default value is ‘Meters’.

source_database

Optional String. Keyword indicating the source data that will be used in the analysis. This keyword is an approximation of the spatial resolution of the digital elevation model used to build the foundation hydrologic database. Since many elevation sources are distributed with units of arc seconds, this keyword is an approximation in meters for easier understanding.

  • Finest: Finest resolution available at each location from all possible data sources.

  • 10m: The hydrologic source was built from 1/3 arc second - approximately 10 meter resolution, elevation data.

  • 30m: The hydrologic source was built from 1 arc second - approximately 30 meter resolution, elevation data.

  • 90m: The hydrologic source was built from 3 arc second - approximately 90 meter resolution, elevation data.

The default value is ‘Finest’.

generalize

Optional boolean. Determines if the output downstream trace lines will be smoothed into simpler lines.

The default value is False.

gis

Optional GIS Object instance. If not provided as input, a GIS object instance logged into an active portal with elevation helper services defined must already be created in the active Python session. A GIS object instance can also be optionally explicitly passed in through this parameter.

return_snapped_points

Optional boolean. Determines if a point feature at the watershed’s pour point will be returned. If snapping is enabled, this might not be the same as the input point.

The default value is True.

future

Optional boolean. If True, the result will be a GPJob and results will be returned asynchronously.

Returns

Result object comprised of two FeatureSets - one for watershed_area, and another for snapped_points

# USAGE EXAMPLE: To identify catchment areas around Chennai lakes.
lakes_watershed = watershed(input_points=lakes_fs,
                            snap_distance=10,
                            snap_distance_units='Meters',
                            source_database='Finest',
                            generalize=False)

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