Missouri | Missouri Ozarks
Big RiverMammoth Access to Merrill Horse Access
Float 5.4 miles from Mammoth to Merrill Horse near De Soto; check Richwoods flow and trend before launch. Allow 2–3.5 hours. Community guidance (not an MDC paddling band) flags scraping below about 100 cfs, a caution zone above about 800 cfs, and no general recommendation above 1,200 cfs.
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Route location
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Route overview
Trip details
Access rules, camping and seasonal notes.
Permits, camping and season
Access and shuttle
Launch at MDC Mammoth Access and take out at MDC Merrill Horse Access for a 5.4-mile Big River day west of De Soto. Use the Richwoods USGS gauge as the direct corridor gauge and skip this route when it is above the local high-water cutoff.
Access map
Put-in
Mammoth AccessMammoth and Merrill Horse are MDC public access areas, but posted signs, road conditions, parking areas, and area maps control exact use.
Take-out
Merrill Horse Access / Highway H bridgeThe Mammoth coordinate is a public paddling-location coordinate paired with MDC access confirmation; the Merrill Horse coordinate uses the USGS Richwoods / Highway H gauge corridor as the practical take-out anchor. Follow on-site signs for the actual ramp or landing.
Road shuttle
Use a short two-car shuttle between MDC Mammoth Access off Mammoth Road and MDC Merrill Horse Access / the Highway H bridge west of De Soto. Stage and inspect Merrill Horse first because it is the planned take-out and also the Richwoods gauge corridor.
Additional access notes
- The app uses community threshold guidance from OzarkAnglers, not an official MDC paddling band. Make a same-day visual call before committing.
More route and safety guidance
- At higher or rising levels expect strong current, muddy water, floating wood, root wads, strainers, and harder gravel-bar landings. The 800-1,200 cfs range is already a caution zone for inexperienced paddlers; do not treat the short distance as a substitute for a same-day visual call.
- Mammoth and Merrill Horse are public MDC access areas, but the Merrill Horse coordinate follows the Richwoods/Highway H corridor rather than a guaranteed ramp point. Stage and inspect the take-out, follow posted area rules, and do not use private banks or informal pull-offs as a substitute.
Plan this paddle
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Conditions
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Recent trend
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Gauge source
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Weather
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Next 8 hours
Short-route forecast
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Plan ahead
Tomorrow and the weekend
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Station details and river cameras
Station observations
USGS measurements
Measurement notes and coverage
These are observations at the station. Water depth and current can differ along your trip.
River camera · USGS
View at the gauge
Big River near Richwoods, MO. This view may be outside your paddling reach. Images are periodic and do not establish safe conditions.
Photos and recent reports
Look for recent access, obstruction and hazard observations. Context photos may show a different part of the river.
Paddler reports
Recent notes from paddlers
A few quick notes from people who were on this route recently.
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Sources and methodology
Review source dates and published guidance below. We have not inspected this trip in person.
Why this scoreData reliability: checking
This rating reflects whether the gauge measures this part of the river, whether published water-level guidance is available, and how recently the data was updated.
- Checking data sources and update times.
- Checking evidence cautions.
Data behind the scoreWater levels, published guidance and update times
These readings and published water-level limits help explain today’s score.
| Gauge site | Big River near Richwoods, MO |
| Discharge | Checking |
| Gauge height | Checking |
| 24h trend | Checking |
| 24h change | Checking |
| Current band | Checking |
| Rain last 24h | Checking |
| Rain last 72h | Checking |
| Air temp | Checking |
| Water temp | Checking |
| Wind | Checking |
| Gusts | Checking |
| Rain timing | Checking |
| Preferred range | 100 cfs to 800 cfs |
| Low threshold | 100 cfs |
| High threshold | 1,200 cfs |
| Evidence strength behind the range | Local route guidance |
| Gauge observed | Checking |
| Paddle Today updated | Checking |
| Main source behind this score | OzarkAnglers Big River section guidance for the Richwoods gauge |
| Gauge source | Checking |
| Weather source | Checking |
| Rainfall source | Checking |
NotesPublished evidence and verification notes
These notes cover the access details, route quirks, and source caveats most likely to matter once you get there.
- Public put-inMDC Mammoth Access
MDC says Mammoth Access is on the Big River, was acquired to provide better public access, and is 5.40 river miles upstream from Merrill Horse Access and the Route H bridge.
- Public take-outMDC Merrill Horse Access
MDC says Merrill Horse Access is on the Big River, 5.40 river miles downstream from Mammoth Access and 5.30 miles upstream from Browns Ford Access, with public department-area boat-use rules.
- Route shapeMammoth to Merrill Horse, 5.4 miles
OzarkAnglers lists Mammoth MDC Access at mile 0.0 and Merrill Horse MDC Access at mile 5.4 for this Big River section. MDC independently gives the same spacing.
- Gauge check during route review · June 1, 2026USGS 07018100
This reading was saved when we checked the guide. It is not today’s water level. Check the current gauge and local conditions before paddling.
- Gauge fitRichwoods / Highway H corridor
OzarkAnglers identifies the Richwoods gauge as the reliable gauge for the Mammoth / Merrill Horse section. USGS site metadata places the gauge at 38.159611, -90.706056, effectively in the Merrill Horse / Highway H take-out corridor.
- Threshold bands100-800 cfs ordinary float window, 1,200 cfs too high
OzarkAnglers describes under 100 cfs as low but floatable with scraping, 100-800 cfs as floatable, 800-1,200 cfs as very high and dangerous for inexperienced paddlers, and over 1,200 cfs as too high.
Verify it yourselfCheck the source links
Use these links to double-check the gauge, route details, and access notes before you head out.
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