Classification: false_positive Confidence: Model confidence should remain 'medium' or potentially drop to 'low' until the overprediction bias is corrected. The current calibrated coefficients are clearly invalid for high-intensity saturated events.
The model massively overpredicted the flood peak (16.05 ft vs 8.35 ft actual) despite intense rainfall and saturated soils, indicating that current response coefficients are too high for this watershed's capacity.
| Metric | Predicted | Actual | Error |
|---|---|---|---|
| Peak height | 16.05 ft | 8.35 ft | +7.70 ft |
| Total rise | — | 7.27 ft | — |
| Band | Zone | Precip | Predicted Rise | Intensity | Moisture |
|---|---|---|---|---|---|
| 1 | upper_richland | 3.84" | 12.49 ft | INTENSE | SATURATED |
| 2 | falling_water | 3.63" | 8.70 ft | INTENSE | SATURATED |
Headline: WATCH — Recent rainfall is within the typical range of historical rises to MEDIUM Settled outcome: None (reached None) LLM said headline was correct: True Notes: The empirical headline predicted a rise to 'MEDIUM' (4.0-6.0 ft range, though the threshold definition in the prompt says medium is 4.0, high is 6.0). The actual peak was 8.35 ft, which exceeds the 'high' threshold. However, the headline warned of rises to MEDIUM. Since the gauge reached well into the higher tiers, the 'watch' warning was valid but conservative. The headline was 'low confidence' for 'medium'. The actual outcome was higher than medium. In the context of 'was the headline borne out', the direction of risk was correct, though magnitude was higher. I will mark this as correct because it successfully flagged a significant event risk, even if it underestimated the severity tier.
This event was a significant hydrological mismatch. The predictor forecasted a 16.05 ft peak based on ~3.8 inches of intense rainfall in saturated conditions, but the gauge only reached 8.35 ft. This represents a 92% overprediction error. The hydrograph showed a multi-pulse rise reaching a high peak (above the 6.0 ft optimal threshold), confirming the rainfall was impactful, but the volume/stage relationship in the model is severely broken at high intensities.
The primary driver of the error is the excessive response coefficients in saturated/intense conditions. The model applies a 2.0x moisture multiplier and 1.4x intensity multiplier, compounding to a 2.8x effective sensitivity on top of base coefficients. Given the peak was less than half the predicted value, the total system response is too aggressive. The timing error (1.3 hours late prediction) is acceptable given the complex multi-pulse nature of the storm, but the magnitude failure is critical.
Recommendations focus on reducing the response sensitivity. Both bands contributed significantly to the prediction (Band 1: 12.49 ft, Band 2: 8.70 ft). Since the actual peak was 8.35 ft, even Band 2's contribution alone nearly matches the observed peak, suggesting Band 1's contribution was largely nonexistent in reality or highly attenuated. We must reduce both band coefficients to reflect the watershed's inability to convey that much volume to stage height, even in saturated states. A conservative 20% reduction is applied to both bands to begin correcting this over-sensitivity.
| Band | Change | Reason |
|---|---|---|
| 1 | -20% | Massive overprediction of contribution from upper headwaters; reducing coefficient to better align predicted stage with observed 8.35 ft peak. |
| 2 | -20% | Overprediction of tributary contribution; reducing coefficient as total system response was nearly half of predicted value. |
Model confidence should remain 'medium' or potentially drop to 'low' until the overprediction bias is corrected. The current calibrated coefficients are clearly invalid for high-intensity saturated events.