Surface Velocity Tools (SurfVelTools)¶

SurfVelTools is a 12,000-line Python application that operationalizes the entropy-based Probability Concept method for computing stream discharge from surface velocity observations. It is the first operational entropy-based discharge computation system deployed in a national water monitoring agency.

Source Code DOI

Overview¶

SurfVelTools computes parameters associated with the Probability Concept method using velocity profile data collected where the maximum in-channel velocity occurs. It also computes streamflow for a given Probability Concept result given a known cross-sectional area, phi, and surface velocity — all variables measured in the field at a typical surface velocimetry gage.

Key Capabilities¶

• Entropy parameter estimation — practical procedures for natural channels
• Uncertainty quantification — methods appropriate for operational settings
• Profile fit evaluation — automated assessment of velocity profile quality
• Multi-sensor input — integrates radar and camera velocity data
• USGS data compatibility — outputs for NWIS streamflow computation and submission
• Archival and export — results can be archived for recordkeeping

Operational Advantages¶

The Probability Concept method offers significant operational improvements:

• Rapid deployment — installation typically complete in 2 days with discharge immediately computed (vs. years for rating development)
• Reduced site visits — 3–5 visits annually vs. 4–8 for conventional methods
• Safe flood measurement — bridge-mounted sensors enable measurements without personnel deployment
• Continuous monitoring — 15-minute discharge records from permanently mounted sensors
• Drone workflow — 90-minute deployment vs. 3–4 hours for conventional measurements

Impact¶

• Deployed nationally as official USGS tool
• Documented in USGS Techniques and Methods report (TM 3-A26)
• Used at multiple gages with both radar and camera inputs
• Applied during major floods for discharge data that contact methods could not obtain
• Base algorithms being adopted in other USGS software (e.g., QRev)

Citation¶

Engel, F.L., 2023, Surface Velocity Tools (SurfVelTools): U.S. Geological Survey software release, doi:10.5066/P9I5JABK.

Technology¶

Python · Qt5 · NumPy · SciPy · lmfit