Classification: partial Confidence: The model has correctly classified 4 consecutive events prior to this one. This event, while partially correct, highlights a need for slight upward calibration of the response coefficient to handle moderate rises more accurately. Confidence remains low as we have not yet met the 5-event threshold for medium confidence.
The physics model underestimated the peak flow by 22.7% during a moderate rainfall event under normal antecedent moisture conditions, though the timing prediction was within acceptable limits.
| Metric | Predicted | Actual | Error |
|---|---|---|---|
| Peak CFS | 78 CFS | 101 CFS | -23 CFS |
| Total rise | — | 65.2 CFS | — |
| Band | Zone | Precip | Predicted Rise | Intensity |
|---|---|---|---|---|
The physics model predicted a peak of 78.1 CFS, while the actual peak reached 101.0 CFS, resulting in an underestimation of 22.9 CFS (-22.7%). This exceeds the ±15-20% threshold for a 'correct' classification, placing it in the 'partial' category as the direction was correct but magnitude was off. The timing error was minimal at 0.4 hours, indicating the lag and dispersion parameters are reasonably accurate for this basin. The rainfall was distributed throughout the day with moderate intensity peaks, and the antecedent moisture was classified as NORMAL, applying a 1.0 multiplier.
The underestimation suggests the current response coefficient of 200 CFS/inch may be slightly low for events of this magnitude and intensity profile. Given the steep nature of the Boxley drainage, small errors in coefficient can compound. A conservative adjustment is warranted to bring the prediction closer to the observed reality without overcorrecting based on a single event.
| Band | Change | Reason |
|---|---|---|
| 1 | +15% | Predicted peak was 22.7% low. Increasing response coefficient by 15% to better capture the runoff efficiency of the steep basin under moderate rainfall intensities, staying within the 20% max adjustment constraint. |