Missouri | Missouri Ozarks

Big River

Mammoth Access to Merrill Horse Access

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Today

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Today's conditions

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Quick facts

On-water distance About 5.4 mi Mammoth Access to Merrill Horse Access

Difficulty easy At ordinary levels this is a short recreational Big River float with gravel riffles, wooded bends, anglers, and MDC access points. It should not be treated as easy when the Richwoods gauge is high or rising, especially above the local 800 cfs caution band.

Shuttle Car 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.

Permits None noted No route-specific paddling permit is known. Follow MDC area rules, posted signs, department-area boat-use rules, access hours, and parking restrictions at both public accesses.

Camping Options nearby Treat this as a short day float. Do not plan on camping at either access unless current MDC signage and area rules explicitly allow it, and do not use private banks without permission.

Season Mar-Nov Spring through fall is the normal paddling window. This short reach can scrape during summer low water, while rain can quickly push it into high, muddy, debris-filled water where the current is unsuitable for casual groups.

Plan

Dial in the shuttle, distance, and access.

Use this section once the route looks viable and you need to turn it into an actual trip plan.

Access plan

Access, shuttle, and map

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.

Directions Apple Maps OpenStreetMap

Start

Put-in

Mammoth Access Open map

Mammoth and Merrill Horse are MDC public access areas, but posted signs, road conditions, parking areas, and area maps control exact use.

Finish

Take-out

Merrill Horse Access / Highway H bridge Open map

The 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.

Pulling access map tiles. Usually under 5 seconds.

Access caveats

Mammoth and Merrill Horse are MDC public access areas, but posted signs, road conditions, parking areas, and area maps control exact use.
The 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.
The app uses community threshold guidance from OzarkAnglers, not an official MDC paddling band. Make a same-day visual call before committing.

Watch for

Scraping and shallow riffles when the Richwoods gauge is near or below 100 cfs.
High or rising water above about 800 cfs, with strong current, muddy water, floating wood, and harder landings.
Flows over 1,200 cfs at Richwoods; local guidance calls this section too high.
Anglers, jetboats or small motorboats, gravel bars, wooded bends, root wads, strainers, and private banks away from public accesses.

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Sources

Check the data behind today's call.

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Why this score Today's data confidence is checking

Data confidence mostly comes down to three things: how direct the gauge is, how clear the range is, and how fresh the data is.

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Outlook Tomorrow and weekend

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Data behind the score Gauge, thresholds, and timing

These are the live readings and threshold notes behind 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
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Air temp	Checking
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Target band	100 cfs to 800 cfs
Low threshold	100 cfs
High threshold	1,200 cfs
Data confidence 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

Notes What to know before you go

These notes cover the access details, route quirks, and source caveats most likely to matter once you get there.

Public put-in MDC 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.

Source
Public take-out MDC 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.

Source
Route shape Mammoth 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.

Source
Direct live gauge USGS 07018100

USGS Big River near Richwoods showed same-day June 1, 2026 values of 1,490 cfs and 5.76 ft at 07:00 CDT during review.

Source
Gauge fit Richwoods / 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.

Source
Threshold bands 100-800 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.

Source

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Quick answers

Big River paddling FAQ

What water level is good for paddling Big River?

Paddle Today watches Big River near Richwoods, MO and treats 100 cfs to 800 cfs as the target band for this route, with weather and recent trend included in the final score.

Where does this Big River route start and end?

This route starts at Mammoth Access and ends at Merrill Horse Access / Highway H bridge, about About 5.4 mi on the water.

Is this Big River route good for beginners?

This is listed as an easy route, but conditions still matter. Check today's score, water level, weather, and access notes before you go.

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