This is a major, watershed-wide rainfall event. April 4 brought 1.2-1.95" across essentially every HUC12 in the watershed — the most widespread significant rainfall since Event 2 (March 7-8).
Spatial pattern: Rain was heaviest in the upper watershed and Richland/Cave Creek zones, with a slight west-to-east gradient: - Boxley zone: 1.574" (peak 0.552"/hr at 08:02 UTC = ~3 AM CDT) - Ponca zone: 1.574" average (peak Beech Creek 1.666" at 0.736"/hr) - Pruitt zone: 1.393" (Cove Creek 1.42", Hoskin Creek 1.37") - St. Joe zone: 1.58" average — highly uniform across sub-groups: - Little Buffalo complex: 1.48-1.95" (Shop Creek 1.95" highest in watershed) - Big Creek complex: 1.45-1.70" - Cave Creek: 1.68" - Richland outlet: 1.62" - Mainstem misc: 1.40-1.58" - Richland zone: 1.647" (Headwaters RC 1.72", Falling Water 1.58") - Bear Creek zone: 1.286" (Headwaters 1.27", Outlet 1.31") - Harriet zone: 1.347" (Dry Creek 1.46" highest) - Ungauged: 1.363"
Timing: Rainfall peaked between 08:02-10:02 UTC (3-5 AM CDT April 4), with the western/upper watershed peaking slightly earlier (08:02 UTC) and eastern/lower areas peaking at 09:02-10:02 UTC. Most rain fell over a 12-hour window — the max_12hr values are essentially identical to totals.
Peak intensities: Highest at Shop Creek (0.811"/hr), Beech Creek (0.736"/hr), Cave Creek (0.712"/hr), Headwaters Big Creek (0.688"/hr), Headwaters Richland (0.649"/hr), Rocky Hollow (0.656"/hr). These are moderate intensities — not as extreme as Event 2's 0.961"/hr peaks but sustained over a longer period.
Antecedent conditions: This is critical — the 7-day precip at the start of today reflects the April 2-3 rain. Richland zone was already at 1.07" 7-day, Bear Creek at 0.84", Cave Creek at 0.82". The April 2-3 rain had already "primed" the lower/southeastern watershed, and this April 4 storm piled on top. For the upper watershed (Boxley 0.52", Ponca 0.35-0.42"), antecedent was still moderate. This is effectively a compound event where the April 2-3 lower-watershed rain created moderate antecedent conditions, and the April 4 storm was widespread and intense.
This is a confirmed Tier 2 (Recreational Response) event at all gauges, with potential Tier 3 elements still developing at St. Joe. Event is still rising at Pruitt and St. Joe at end of day.
| Gauge | Pre-Event (start 4/04) | Peak (or latest) | Rise | Peak/Latest Time | Status |
|---|---|---|---|---|---|
| Boxley | 1.84 ft | 3.89 ft | +2.05 ft | 14:15-15:15 CDT | Receding (3.56 ft) |
| Ponca | 87.8 cfs | 823 cfs (+837%) | +735 cfs | ~16:00 CDT | Receding (503 cfs) |
| Pruitt | 3.45 ft / 48 cfs | 5.97 ft / 867 cfs | +2.52 ft / +819 cfs | 23:15 CDT | STILL RISING |
| St. Joe | 3.43 ft / 169 cfs | 5.01 ft / 801 cfs | +1.58 ft / +632 cfs | 22:45 CDT | STILL RISING sharply |
| Harriet | 3.59 ft / 197 cfs | 3.88 ft / 336 cfs | +0.29 ft / +139 cfs | ~18:00 CDT | Plateau/slight rise; expect more |
| Richland | 0.99 ft | 3.58 ft | +2.59 ft | ~17:45 CDT | Receding (3.30 ft) |
| Bear Creek | 2.28 ft / 4.6 cfs | 3.53 ft / 203 cfs | +1.25 ft / +198 cfs (+4300%) | ~15:00 CDT | Receding (3.36 ft / 143 cfs) |
Detailed timing analysis:
Boxley: Rise began ~02:45 CDT (1.84→1.87 ft in 15 min). Accelerated sharply from 07:45 CDT through 11:15 CDT (peak hourly rise 0.51 ft/hr). Peaked at 3.89 ft from ~14:15-15:15 CDT, then began steady recession at ~0.04-0.06 ft/hr. Currently 3.56 ft and falling.
Local knowledge comparison: Boxley peaked at 3.89 ft. Per local knowledge, the Boxley-Ponca section is Optimal at 3.7 ft and High at 5.0 ft. The Hailstone (above Boxley) is Low-but-Floatable at 3.7 ft, Optimal at 4.4 ft, and High at 5.9 ft. So Boxley-Ponca was in Optimal range from approximately 13:00 to well past end of day (still 3.56 ft). The Hailstone was in Low-but-Floatable from ~13:00 CDT and briefly approached Optimal but didn't quite reach 4.4 ft. This is the first time this study has observed Boxley above 3.2 ft (the previous high was 3.28 ft in Events 2 and 3).
Ponca: Rose from 87.8 cfs gradually starting ~03:00 CDT, accelerated sharply from ~10:45 CDT (188→823 cfs peak at ~16:00 CDT). Ponca crossed into Low-but-Floatable (>150 cfs) at ~09:45 CDT, into Optimal (>200 cfs) at ~11:00 CDT. Peaked at 823 cfs — well into Optimal, nowhere near Flood (1600 cfs). Now receding (503 cfs at 23:15 CDT) but still solidly in Optimal range.
Pruitt: Two distinct phases visible: 1. Slow rise from local Pruitt-zone rain (03:00-20:00 CDT): 3.42→3.87 ft over 17 hours = +0.45 ft. Discharge rose from ~48 to ~124 cfs. This is the direct runoff from 1.39" falling on Cove Creek/Hoskin Creek HUC12s. 2. Sudden surge from mainstem propagation (20:15-23:15 CDT): 3.98→5.97 ft in 3 hours = +1.99 ft, discharge 150→867 cfs. This is the Ponca peak wave arriving. The transition is dramatic — from 3.87 ft at 20:00 to 4.40 ft at 20:30 to 5.10 ft at 20:45. Pruitt is still rising at end of day (5.97 ft / 867 cfs). Pruitt crossed Optimal (>200 cfs) at ~20:30 CDT and is well within Optimal range (threshold 2000 cfs for Flood).
St. Joe: Steady, progressive rise throughout the day in two overlapping phases: 1. Early rise from local St. Joe zone runoff (04:00-14:00 CDT): 3.45→3.64 ft / 175→231 cfs. Gentle, continuous. St. Joe entered Optimal (>200 cfs) at ~07:00 CDT. 2. Accelerating rise from combined tributary + Richland inputs (14:00-22:45 CDT): 3.64→5.01 ft / 231→801 cfs. The acceleration after ~21:30 CDT is sharp (4.14→5.01 ft in 75 minutes = 0.78 ft/hr max).
Signal separation at St. Joe: Richland Creek surged dramatically (0.99→3.58 ft, peak ~17:45 CDT). This confirms substantial Richland sub-basin contribution to St. Joe's rise. The Richland peak preceded the sharp St. Joe acceleration by ~4 hours, consistent with travel time from the Richland confluence to St. Joe gauge. However, the St. Joe was already rising before Richland peaked, indicating contributions from other tributaries (Big Creek, Little Buffalo, Cave Creek all received 1.4-1.95"). This is a multi-source St. Joe event — unlike the March 2024 reference event which was Richland-dominated, this has contributions from virtually all 14 HUC12s.
Richland Creek: Rose from 0.99 ft to 3.58 ft (+2.59 ft). Per local knowledge, Upper Richland is Low-but-Floatable at 3.2 ft, Optimal at 4.0 ft, and High at 6.0 ft. Richland entered Low-but-Floatable at ~10:00 CDT and nearly reached Optimal (~3.58 peak vs 4.0 threshold). This confirms the local knowledge that Richland runs are rare — 1.65" of rain on moderate antecedent just barely puts it into the boatable range.
The rise timing: Initial slow rise 00:30-03:45 CDT (0.99→1.04, from prior day's rain continuing to arrive). Then rapid rise from ~04:00 CDT (response to today's peak rainfall at ~03-04 AM CDT), with an explosive jump visible between 05:15 and 07:00 (data gap, but went from 1.25→2.05 ft). Peaked at 3.58 ft ~17:45 CDT. Now receding.
Bear Creek: The most dramatic percentage response. From 2.28 ft / 4.6 cfs to 3.53 ft / 203 cfs — a +4,300% discharge increase. Rise began subtly from April 3's late-evening rain (2.28→2.34 by 04:15 CDT). Then a second, much larger pulse: relatively stable at 2.38 ft through 12:45 CDT, then explosive rise to 3.09 ft at 13:15 CDT, 3.41 ft at 13:45, peaking at 3.53 ft at 15:00 CDT. The surge from 2.38→3.09 ft in 15 minutes (13:00-13:15) is the fastest rise rate observed at Bear Creek this study. Now receding (3.36 ft / 143 cfs).
The Bear Creek response timing is interesting: today's rain peaked at 10:02 UTC (5 AM CDT) in the Bear Creek zone. The initial response appeared at ~04:00 CDT (from last night's continuing rain), but the major surge didn't arrive until ~13:00 CDT — roughly 8 hours after peak rainfall. This is the first significant Bear Creek event in the study.
Harriet: Steady, smooth rise from 3.59→3.88 ft / 197→336 cfs. Entered Optimal (>200 cfs) at ~04:15 CDT from local Harriet-zone runoff (1.35" average). Currently plateauing around 3.87-3.88 ft — but the mainstem wave from St. Joe hasn't arrived yet. Based on Event 2's St. Joe→Harriet lag of ~7 hours, and St. Joe is still rising sharply at 22:45 CDT, Harriet should see a significant additional rise beginning April 5 morning (~05:00-08:00 CDT).
Bear Creek signal separation at Harriet: Bear Creek is independently surging (203 cfs peak), which contributes directly to Harriet. But Harriet's current rise appears dominated by its own local HUC12 runoff plus the earliest Bear Creek contribution. The major mainstem propagation from upstream is still incoming.
Boxley: 1.574" → +2.05 ft rise. Response ratio: 1.30 ft/inch. Antecedent: moderate (0.52" 7-day from April 2). Compare to: Event 1 (1.04" → +0.87 ft = 0.84 ft/inch on wet), Event 2 (1.14" → +0.81 ft = 0.71 ft/inch on wet), April 2 (0.52" → +0.12 ft = 0.23 ft/inch on extreme dry). The 1.30 ft/inch today is the highest response ratio observed at Boxley — surprising given antecedent wasn't particularly wet. However, the April 2 rain (0.52") had already "filled the pools" per local knowledge, converting the extreme-dry antecedent to moderate. This is strong evidence that the pool-filling effect is real and the April 2 rain served as the "primer." The 36-hour delay from April 2 rain was the pool-filling phase; today's heavier rain arrived on already-primed pools and produced the strongest response ratio yet.
Lag time at Boxley: Rain peaked at ~03:02 AM CDT (08:02 UTC). Boxley rise onset was ~02:45 CDT — essentially simultaneous, suggesting the earliest rain was already producing runoff. The steepest rise occurred 08:00-11:00 CDT, about 5-8 hours after peak rainfall. Peak at ~14:15 CDT, about 11 hours after peak rain. This is much faster than the 36-hour pool-filling response from April 2's rain (0.52" on extreme dry), confirming that once pools are filled, Boxley responds within hours.
Richland Creek: Combined April 3+4 rain: 0.62" + 1.65" = ~2.27" over 2 days. Rise from pre-event 0.95 ft (Day 34 mid-afternoon) to 3.58 ft = +2.63 ft. Attributing most response to today's 1.65" with the 0.62" as antecedent priming: response ratio ~1.59 ft/inch — the strongest response observed at any gauge this study. This makes sense: Richland had already received 0.62" the prior evening (moderate priming on what was dry antecedent), then 1.65" hit.
Bear Creek: Combined April 3+4 rain: 0.67" + 1.29" = ~1.96" over 2 days. Rise from pre-event 2.28 ft / 4.6 cfs to 3.53 ft / 203 cfs = +1.25 ft / +198 cfs. Response ratio: ~0.97 ft/inch (using today's 1.29" as primary input). This is the first quantifiable Bear Creek rainfall-response pair. The lag time from peak rainfall (05:02 CDT) to peak gauge (15:00 CDT) is approximately 10 hours — longer than Richland's ~7-hour lag for similar rainfall, possibly reflecting Bear Creek's larger drainage area (239 vs 174 km²) or different karst/storage characteristics.
Ponca: Zone average 1.57". Pre-event 87.8 cfs, peak 823 cfs = +735 cfs (+837%). Ponca's drainage includes Boxley upstream plus Beech Creek, Smith Creek, and Whiteley Creek. The delayed Ponca surge (sharp acceleration starting ~10:45 CDT) reflects the Boxley wave arriving plus local tributary inputs. Response ratio in discharge: ~468 cfs/inch — compare to Event 2 (1.92" → +1975 cfs = 1029 cfs/inch on wet) and Event 3 (0.83" → +350 cfs = 422 cfs/inch on wet). Today's 468 cfs/inch on moderate antecedent is between the wet-antecedent Events 2 and 3 values, which is consistent.
Clear propagation sequence visible, though event is still developing:
Boxley→Ponca: - Boxley rise onset: ~02:45 CDT - Ponca rise onset: ~03:00 CDT (almost simultaneous — both receiving local rain) - Boxley sharp acceleration: ~07:45 CDT - Ponca sharp acceleration: ~10:45 CDT → lag ~3 hours - Boxley peak: ~14:15 CDT - Ponca peak: ~16:00 CDT → lag ~1.75 hours
The lag is shorter than Events 1-3 because Ponca was also receiving its own heavy rain (1.57" on Ponca zone) simultaneously. The "wave" from Boxley arrives on top of already-rising local runoff. The Boxley peak to Ponca peak lag of ~1.75 hours at ~600-800 cfs transit flow is faster than previous events (4-5 hours at 150 cfs in Event 1).
Ponca→Pruitt: - Ponca peak: ~16:00 CDT (823 cfs) - Pruitt surge onset: ~20:15 CDT (transition from slow local rise to rapid propagation wave) - Lag: ~4.25 hours at ~800 cfs transit flow
This provides a 5th data point for the Ponca→Pruitt velocity relationship. At ~800 cfs transit flow, the 4.25-hour lag gives velocity ~1.6 m/s. Previous data: 5.75 hr at ~1500-2000 cfs (Event 2, velocity ~1.2 m/s), 7.5 hr at ~400-500 cfs (Event 3, velocity ~0.93 m/s), 14-15 hr at ~150-180 cfs (Events 1 and Day 15, velocity ~0.46-0.50 m/s). Wait — the 4.25-hour lag at ~800 cfs produces a faster velocity than Event 2 at ~1500-2000 cfs? This warrants careful consideration. Possible explanations: (a) Pruitt was receiving its own local rain simultaneously, so the "surge onset" at 20:15 may include both propagation and local acceleration overlapping; (b) the transit flow during this event may be higher than estimated because Pruitt zone was already receiving heavy local runoff. I'll flag this as uncertain — the overlap of local Pruitt runoff with the propagation wave makes it difficult to cleanly separate the arrival time.
Pruitt→St. Joe: Still developing. Pruitt is still rising at 23:15 CDT. St. Joe is also still rising, but its rise has been continuous since early morning from local tributary inputs (Richland, Big Creek, Little Buffalo, Cave Creek all receiving 1.4-1.7"). The Pruitt wave arrival at St. Joe won't be cleanly separable from the ongoing local tributary inputs. This event will be challenging for Pruitt→St. Joe propagation analysis.
St. Joe→Harriet: Not yet observable. St. Joe still rising. Expect Harriet to show the upstream wave beginning April 5 morning.
This is now a confirmed 3-day compound event (April 2-3-4). The April 2 upper-watershed rain (0.5") primed the pools, the April 3 lower-watershed rain (0.5-0.7") primed Richland/Bear Creek, and the April 4 watershed-wide storm (1.2-1.95") produced the main event response.
Updated compound event classification: This is now clearly Tier 2 (Recreational Response) and potentially approaching Tier 3 (High Water) at Pruitt, depending on how high Pruitt peaks. Current 867 cfs is well below the 2,000 cfs Flood threshold but rising. If Pruitt's rise continues for a few more hours, it could approach 1,000+ cfs. St. Joe at 801 cfs is solidly in Optimal (threshold 8,000 for Flood).
Recreational significance: This is the most consequential recreational event since Event 2 (March 7-8): - Boxley-Ponca section: Optimal for many hours (3.56 ft falling, still above 3.2 Low-but-Floatable at EOD) - Ponca-Pruitt: Optimal from ~11:00 CDT - Pruitt: Currently 867 cfs, solidly Optimal (200-2000 range), still rising - St. Joe: Entered Optimal at ~07:00 CDT, 801 cfs rising - Harriet: Entered Optimal at ~04:15 CDT (200 cfs), currently 336 cfs, more to come - Richland Creek: Reached Low-but-Floatable (3.2 ft) at ~10:00 CDT, peaked 3.58 ft — per local knowledge this is a rare boatable run that occurs only 3-7 times per year
Boxley response ratio of 1.30 ft/inch is the highest observed. This exceeds even the wet-antecedent events (0.71-0.84 ft/inch). The hypothesis would predict wet-antecedent should produce the highest ratios, but antecedent here was only moderate (0.52" 7-day). Possible explanation: the April 2 rain specifically filled the pools (per local knowledge), creating an effectively "primed" condition that's different from broadly wet antecedent. The pool-filling hypothesis is supported — what matters isn't total 7-day moisture but whether the upstream pools are full. After 22 days of drought, 0.52" may have been exactly enough to fill the pools but not saturate the broader watershed, producing a high ratio for the subsequent storm.
Richland Creek reached boatable level on 1.65" with moderate antecedent. Per local knowledge, this is a 3-7 times/year event. Today's conditions (1.65" on 0.55" 7-day antecedent = moderate) produced peak 3.58 ft vs 3.2 ft Low-but-Floatable threshold. This gives us a first calibration point: ~1.5-1.7" on moderate antecedent is the approximate threshold for a Richland Creek boatable run. On dry antecedent, likely 2.0-2.5"+ would be needed.
Bear Creek's explosive response (4.6→203 cfs, +4300%) from 1.29" (today) + 0.67" (yesterday) is by far the largest Bear Creek response. The transition from 9.93 cfs at 12:45 to 75.8 cfs at 13:15 (a 15-minute 7.6x jump) suggests a threshold-type behavior — possibly karst springs activating or surface runoff suddenly dominating over infiltration.
Ponca→Pruitt propagation timing anomaly: The apparent 4.25-hour lag at ~800 cfs doesn't fit the established velocity-discharge relationship well (it suggests faster velocity at lower flow than Event 2). This is likely due to simultaneous local Pruitt runoff masking the true wave arrival. I'll note this as uncertain in the hypothesis.
St. Joe's rise is notably slower than Richland's despite similar rainfall. St. Joe at 5.01 ft / 801 cfs vs Richland at 3.58 ft (receding). Richland surged 2.59 ft in ~14 hours; St. Joe has risen only 1.58 ft in ~19 hours. This reflects St. Joe's massive 1,342 km² drainage area smoothing and spreading the hydrograph — runoff from 14 different HUC12s arrives at different times, producing a broader, lower peak than a concentrated single-tributary event. Compare to the March 2024 reference event where concentrated Richland-zone rain produced an 11-ft rise at St. Joe — that event had 4-8" vs today's 1.6", and was concentrated rather than distributed.