Zero precipitation today across the entire watershed. All 37 HUC12s report 0.0" for the 24-hour period. All gauge-mounted rain gauges also report 0.0" (Pruitt, St. Joe, Harriet, Bear Creek). This is a clean dry day — ideal for tracking the recession limb of Event 4 without interference from new inputs.
7-day antecedent precipitation remains elevated from the April 4 storm: highest in Richland headwaters (2.787"), Cave Creek (2.499"), Big Creek headwaters (2.355"), and Boxley headwaters (2.301"). The lower watershed zones are also wet at 1.4-2.1". This is the wettest antecedent condition since the Event 2 period in early March.
Today is entirely about recession from Event 4 and the continued downstream propagation of the April 4 rainfall pulse. No new rises occurred. The key story is the massive St. Joe and Harriet rises that were still developing at the end of yesterday's data.
Boxley (07055646): Pure recession all day. Started at 3.51 ft (midnight), fell steadily to 3.03 ft by 22:30, a decline of 0.48 ft over ~23 hours. Recession rate averaged ~0.02 ft/hr, slowing from ~0.07 ft/hr early to ~0.01 ft/hr by end of day. Per local knowledge, Boxley remained above 3.2 ft (Boxley-Ponca floatable threshold) until approximately 13:00 CST — roughly 24 hours of Boxley-Ponca floatable conditions from the peak. Above 3.0 ft all day, so still well above the Hailstone minimum (3.7 ft was exceeded yesterday but is now past). The Boxley-Ponca section was floatable for approximately the first 13 hours of today.
Ponca (07055660): Recession from Event 4 peak. Started at 495 cfs, declined steadily to 277 cfs by 23:30. Remained in Optimal range (200-1600 cfs) all day. Recession rate: ~218 cfs over 23.5 hours = ~9.3 cfs/hr. Ponca remained solidly floatable all day. This is a remarkably sustained elevated flow — 277 cfs at end of day is still well above the 200 cfs Optimal threshold.
Pruitt (07055680): Entered the day at 5.97 ft / 867 cfs (still near peak from late April 4). Clean recession throughout: 5.97 ft → 5.03 ft (-0.94 ft) and 867 cfs → 479 cfs (-388 cfs). Recession rate: ~0.04 ft/hr early, slowing to ~0.02 ft/hr by evening. Pruitt remained in Optimal range (200-2000 cfs) all day. At 479 cfs, it will likely remain in Optimal for at least another day.
St. Joe (07056000): This is the headline gauge today. St. Joe was still rising at the start of the day and didn't peak until mid-day: - 00:00: 5.64 ft / 1,180 cfs (still climbing rapidly) - Rose through the morning: +1.76 ft total rise from start of day - Peak: 7.40 ft / 2,630 cfs at ~12:30 CST - Then began gradual recession: 7.40 → 6.81 ft by end of day (-0.59 ft over ~10 hours) - Ended day at 6.81 ft / 2,080 cfs
The total St. Joe rise for Event 4 (from pre-event baseflow to peak): - Pre-event: 3.38-3.43 ft / ~153-169 cfs (April 3 baseline) - Peak: 7.40 ft / 2,630 cfs - Total rise: ~4.0 ft / ~2,460 cfs (+1,440%)
This is a very significant event at St. Joe — the +4.0 ft rise approaches the +4.60 ft rise from Event 2 (March 7-8), despite Event 4 having lower peak rainfall totals at St. Joe zone gauges. The sustained nature of the widespread 1.3-1.7" rain across all 14 St. Joe HUC12s simultaneously, combined with contributions from Richland Creek and upstream gauges, drove this large response.
St. Joe remained in Optimal range (200-8000 cfs) throughout. At 2,080 cfs at day's end, it's above Event 1 and Event 3 peaks but below Event 2's peak of 3,230 cfs.
Harriet (07056700): The most dramatic rise today — Harriet received the full propagation wave: - 00:00: 3.88 ft / 336 cfs - Rose steadily all day long - Peak: 6.55 ft / 2,720 cfs at ~19:15 CST (height), though CFS peaked at 2,720 at 19:15 and 20:45 - Started barely receding at end of day: 6.48 ft / 2,640 cfs - Total rise: +2.67 ft / +2,384 cfs (+710%)
This is significant because: - Harriet was essentially flat at baseline when St. Joe was already surging - The entire Harriet rise today is from upstream propagation + Bear Creek/local tributary contributions that peaked yesterday - The rise at Harriet was remarkably smooth and gradual — no sharp spike, just a steady 19-hour ramp-up - Harriet remains in Optimal range (200-9370 cfs) but well below flood threshold
Richland Creek (07055875): Pure recession. Started at 3.20 ft, declined to 2.52 ft (-0.68 ft). Per local knowledge, Richland was above 3.2 ft (low-but-floatable for Upper Richland) very briefly — essentially just at the threshold at midnight, then immediately below. The peak from yesterday (3.58 ft) was well into the Optimal range (4.0 ft) per local knowledge — it reached 3.58 ft but not the 4.0 ft optimal threshold, so it was floatable but suboptimal. There are significant data gaps in the Richland time series (missing readings from ~07:30-09:00, ~12:15-14:00, ~17:15-19:00, ~21:15-22:00) which is typical for this gauge.
Bear Creek (07056515): Pure recession. Started at 3.34 ft / 136 cfs, declined to 2.90 ft / 47.5 cfs. Recession rate was very steady — this is a well-behaved exponential decay curve.
No new rainfall today, but we can now complete the Event 4 analysis with the full peak data for St. Joe and Harriet:
St. Joe — Event 4 Complete Response: - Total QPE across St. Joe zone (April 4): ~1.58" average (range 1.4-1.95" across 14 HUC12s), plus prior-day pulses of 0.0-0.7" on April 3 in southeastern sub-basins - Prior pulse rain on April 3 in Richland/Bear Creek/Cave Creek/Calf Creek zones: 0.4-0.7" - Main pulse April 4: 1.3-1.95" across virtually all HUC12s, concentrated in morning hours (peak ~09:02 UTC = 03:02 CST) - Pre-event baseflow: ~165 cfs - Peak: 2,630 cfs at ~12:30 CST April 5 - Lag from QPE centroid (~03:00 CST April 4) to St. Joe peak (~12:30 CST April 5): ~33.5 hours - This is significantly longer than the ~14 hour lag from Event 2's more intense, upper-watershed-weighted storm - Explanation: The rain fell simultaneously across the entire 1,342 km² St. Joe zone, including distant sub-basins (Little Buffalo, Big Creek, Cave Creek, Calf Creek, Richland outlet) that have the longest travel times to the St. Joe gauge. The more distributed rainfall means contributions arrive over a longer period, stretching and flattening the hydrograph compared to a concentrated storm.
Signal Separation Check — St. Joe: - Richland Creek surged (0.99 → 3.58 ft on April 4, now receding through 3.2 → 2.52 today) — confirms heavy rain in Richland HUC12s (0306, 0307: 1.58-1.72") - But Richland was already receding when St. Joe was still rising strongly → the late-arriving contributions to St. Joe are from more distant sub-basins (Little Buffalo complex at 1.48-1.95", Big Creek complex at 1.45-1.70", Calf Creek at 1.58") - The secondary steepening of St. Joe's rise around 08:00-12:30 April 5 (from ~0.02 ft/15min to ~0.04 ft/15min around 09:00-11:00) likely represents the arrival of the Big Creek and Little Buffalo flood waves
Harriet — Event 4 Complete Response: - Total QPE across Harriet's direct zone (April 4): ~1.35" average - Bear Creek (independent tributary): 1.27-1.31" → peaked at 3.53 ft / 203 cfs at ~15:00 CST April 4, now receding - Harriet baseflow: ~172-189 cfs - Harriet peak: 2,720 cfs at ~19:15 CST April 5 - Lag from QPE centroid (~04:00 CST April 4, slightly later peak time in eastern zones) to Harriet peak (~19:15 CST April 5): ~39 hours - Lag from St. Joe peak (12:30 CST April 5) to Harriet peak (~19:15 CST April 5): ~6.75 hours
This St. Joe → Harriet propagation time of ~6.75 hours at high flow is consistent with Event 2's estimate of ~8 hours (which was at somewhat different flow conditions). At this flow level, the ~80 km mainstem distance implies an average wave velocity of ~3.3 km/hr (~0.9 m/s), which is reasonable for a flood wave in a natural channel.
Bear Creek Signal Separation: Bear Creek was independently activated on April 4 (2.28 → 3.53 ft, 4.6 → 203 cfs) and is now receding. This confirms the lower-watershed April 3-4 rain pattern. On April 5, Bear Creek is in pure recession, so the continued Harriet rise is entirely from upstream propagation (mainstem flow from St. Joe + local Harriet-zone runoff).
Event 4 propagation is now well-resolved:
| Segment | Peak-to-Peak Lag | Distance | Wave Speed |
|---|---|---|---|
| Boxley → Ponca | Boxley peak 14:15 Apr 4, Ponca peak ~16:00 Apr 4 | ~30 km | ~17 km/hr |
| Ponca → Pruitt | Ponca peak ~16:00 Apr 4, Pruitt peak ~00:15 Apr 5 | ~20 km | ~2.4 km/hr |
| Pruitt → St. Joe | Pruitt peak ~00:15 Apr 5, St. Joe peak ~12:30 Apr 5 | ~65 km | ~5.3 km/hr |
| St. Joe → Harriet | St. Joe peak ~12:30 Apr 5, Harriet peak ~19:15 Apr 5 | ~80 km | ~11.9 km/hr |
Important caveat on Pruitt → St. Joe: The 12+ hour lag and apparent slow wave speed is misleading. The St. Joe peak is dominated by tributary inputs (Little Buffalo, Big Creek, Richland, Cave Creek) that have their own lag times from rain → St. Joe gauge, NOT by mainstem propagation from Pruitt. The mainstem flow from Pruitt is a minor contributor to the St. Joe hydrograph given that St. Joe's cumulative drainage is 1,932 km² vs. Pruitt's 513 km². The St. Joe peak timing reflects when the sum of all 14 HUC12 contributions maximizes, not when the Pruitt wave arrives.
Ponca peak timing anomaly: Ponca peaked at 823 cfs around 16:00 CST on April 4, only ~2 hours after Boxley peaked at 3.89 ft at ~14:15. However, Ponca then had a secondary rise driven by a very sharp flood pulse arriving at Pruitt around 20:15-21:15 April 4 (Pruitt went from 3.87 ft → 5.66 ft in just 1 hour). This Pruitt pulse appears to be from a delayed local tributary input (likely Cove Creek or Hoskin Creek), NOT from Ponca propagation.
Event 4 is now well past peak at all gauges except Harriet, which barely peaked late today. Final classification:
Event 4 was a three-pulse compound event that became the second-largest event of the study:
| Pulse | Timing | Source Area | Peak Intensity |
|---|---|---|---|
| Pulse 1 | Apr 3 late evening | SE watershed (Bear Creek, Richland, Cave Creek) | 0.4-0.7" |
| Pulse 2 | Apr 4 pre-dawn | Lower watershed (Bear Creek, Harriet) | 0.5-1.0" |
| Pulse 3 | Apr 4 morning | Watershed-wide | 1.2-1.95" everywhere |
The combined effect was dramatically amplified by Pulse 1 wetting the landscape before the main Pulse 3 arrived. The April 3 antecedent was only 0.2-0.6" (7-day), which would normally suggest a moderate response. But the rapid succession of three pulses within 36 hours created near-saturated conditions by Pulse 3.
Comparison to Event 2 (March 7-8):
| Metric | Event 2 | Event 4 | Ratio |
|---|---|---|---|
| Peak QPE zone avg | 2.0" (Pruitt) | 1.58" (St. Joe) | 0.79 |
| Boxley peak | 3.28 ft | 3.89 ft | 1.19 |
| Ponca peak | 2,120 cfs | 823 cfs | 0.39 |
| Pruitt peak | 2,610 cfs | 867 cfs | 0.33 |
| St. Joe peak | 3,230 cfs | 2,630 cfs | 0.81 |
| Harriet peak | 3,050 cfs | 2,720 cfs | 0.89 |
Key observation: The upper gauges (Ponca, Pruitt) show Event 4 was much smaller than Event 2, but the lower gauges (St. Joe, Harriet) show Event 4 was nearly as large. This demonstrates the importance of the distributed mid-watershed rain — the 14 St. Joe HUC12s all contributing 1.3-1.95" simultaneously produced a larger cumulative volume than Event 2's more concentrated upper-watershed storm, even though Event 2 had higher peak intensity.
The Pruitt spike: The sharp rise at Pruitt from 3.87 ft to 5.97 ft (+2.10 ft) in approximately 2 hours (20:15-22:30 April 4) is notable. With only 0.87" measured at the Pruitt rain gauge and the zone average of 1.39", this seems like a disproportionate response. However, with the prior Pulse 1/2 pre-wetting the Cove Creek and Hoskin Creek drainages, the soil was near saturation when the main rain arrived. The extremely steep rise rate (1.68 ft/hr peak) suggests a flash flood response in these small, steep HUC12s — very relevant for Tier 3/4 hypothesis building.
1. Boxley exceeded Hailstone threshold: Per local knowledge, the Hailstone section (upper Buffalo above Boxley) becomes "low but floatable" at 3.7 ft. Boxley reached 3.89 ft on April 4 and was above 3.7 ft from approximately 13:00-18:00 April 4 — roughly 5 hours of Hailstone-floatable conditions. This is noteworthy because locals say it's "runnable only 2-4 times per year" — this is the first confirmed opportunity in our study. By today, Boxley had fallen well below 3.7 ft.
2. Richland Creek approached but did not reach Optimal for Upper Richland paddling: Local knowledge says Optimal is 4.0 ft on the Richland gauge. Richland peaked at 3.58 ft — above the 3.2 ft Low-but-Floatable threshold but below Optimal. For approximately 12 hours (roughly 10:00 April 4 through ~22:00 April 4 based on the available data), Upper Richland was in the Low-but-Floatable range. The 1.65" average across the Richland HUC12s was insufficient to reach Optimal — this provides a calibration point: ~1.6-1.7" widespread rain on moderately dry antecedent (0.3-0.55" 7-day) produces Low-but-Floatable but not Optimal on Upper Richland.
3. Ponca-Pruitt CFS discrepancy persists at high flows: On April 4, Ponca peaked at 823 cfs while Pruitt peaked at 867 cfs — Pruitt slightly higher, which makes physical sense since Pruitt drains more area. However, at the start of today, Ponca was at 495 cfs while Pruitt was at 867 cfs — a 372 cfs difference despite Pruitt only draining 123 km² more through its direct tributaries. This suggests the Pruitt pulse was largely from Cove/Hoskin creek flash response, not from Ponca throughflow. By end of day, the gap narrowed: Ponca 277 cfs vs. Pruitt 479 cfs — Pruitt still 202 cfs higher, consistent with significant ongoing baseflow contribution from Cove/Hoskin creeks during recession.
4. St. Joe secondary acceleration: Between 08:00 and 12:30 April 5, St. Joe showed a notable secondary acceleration in its rise rate (height gain ~0.04 ft/15min vs ~0.02 ft/15min in the 07:00-08:00 period). This occurred while Pruitt and Richland were already well into recession. This timing is consistent with the arrival of Big Creek and Little Buffalo flood contributions, which have the longest travel times to the St. Joe gauge. This confirms the signal separation hypothesis — late-arriving tributary floods from distant sub-basins can steepen the St. Joe hydrograph even after the headwater gauges are receding.