This tool should be designed for the purpose of creating a custom flow file for a desired FIM scenario. Given a flow and feature_id, the tool should trace down the NWM streamlines and assign the input flow to each downstream segment for a specified distance.

Inputs:

• feature_id: starting feature_id
• cfs or cms: input flow to be assigned for every reach. These should be separate optional arguments.
• miles or km: the distance downstream to propagate the flow value. These should be separate optional arguments.

Output:

• flow file: file path for flow file CSV

Some things to consider:

• Use NWPS API to get the routing and distance to avoid HUC boundary data issues
  https://api.water.noaa.gov/nwps/v1/reaches/21687144
• Distance will have to be calculated from the lat/lon from NWPS, which won't be river-mile distance
• Possible to provide gage input
• Example usage: python /foss_fim/tools/custom_flow_file.py -f 21687144 -cfs 200000 -mi 15 -o ./custom_flows.csv