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See all 15 routes on Potomac River

Maryland | Montgomery, Frederick, and Washington Counties / Central Maryland

Potomac River

Williamsport River Bottom Park to Big Slackwater Boat Ramp above Dam 4

Check current paddling conditions for this Potomac River route, including water level, recent gauge trend, weather, and route details.

Route location

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DistanceApproximately 14.4 Potomac river miles from Williamsport to Big Slackwater above Dam 4
DifficultyModerate
Typical time6–10 hours depending on stage
ShuttleCar shuttle
The historic Town Creek Aqueduct crosses the C&O Canal corridor beside the Potomac River in Maryland.
Route photoC&O Canal and Potomac River corridor at Town CreekPhoto by Wikimedia Commons

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Why this call
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Conditions

Gauge history and hourly forecast

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Gauge detail

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Route overview

Quick facts and what's next

Distance, difficulty, shuttle basics, and the near-term outlook before you commit to the drive.

Quick facts

On-water distanceApproximately 14.4 Potomac river miles from Williamsport to Big Slackwater above Dam 4Williamsport River Bottom Park to Big Slackwater Boat Ramp above Dam 4
DifficultymoderateThe source describes recreational moving water, but shallow rock, current, cold water, debris, and bridge or access hazards remain material.
ShuttleCar shuttleStage at Big Slackwater Boat Ramp, confirm the Dam 4 Road approach and parking, then shuttle to Williamsport River Bottom Park. Leave daylight for the power-plant portage, Cumberland Valley/Opequon camping context, wind, and the Big Slackwater take-out; do not block C&O operations.
PermitsCheck posted rulesFollow current Maryland boating/PFD rules, C&O Canal National Historical Park ramp and parking rules, NPS closures, NWS flood products, local launch restrictions, and all posted dam, wildlife, and private-shoreline boundaries. No route-specific paddling permit is claimed.
CampingOptions nearbyCumberland Valley and Opequon Junction are documented C&O hiker-biker camping options along the reach. Confirm current NPS status, vehicle staging, water, fees/reservations, and whether the trip plan can safely reach a campsite; no riverbank camping is included.
SeasonMar-NovSpring through fall is the practical planning season, but Maryland water levels, recent rain, temperature, debris, and daylight control every launch decision.

Plan ahead

Upcoming outlook

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Plan

Plan your trip

Launch points, shuttle details, distance, and access notes.

Route logistics

Access and shuttle

A bounded Class I Western Maryland Potomac reach from the public Williamsport River Bottom Park ramp to the public Big Slackwater ramp above Dam 4. The route is mostly flatwater behind two dams, includes a mandatory early power-plant portage, and ends before the Dam 4 hydraulic hazard.

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Prepare this trip

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Start

Put-in

Williamsport River Bottom Park / Potomac Park boat ramp
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Williamsport River Bottom Park and Big Slackwater are public access areas, but current ramp, parking, road, water-entry, and flood conditions must be confirmed on launch day.

Finish

Take-out

Big Slackwater Boat Ramp above Dam 4
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The two named campsites are not promised boat landings or drive-to bailouts; do not cross private banks or canal structures to shorten the route.

Plan this segment

Pulling access map tiles. Usually under 5 seconds.

Access caveats and watch for

Access caveats

  • Williamsport River Bottom Park and Big Slackwater are public access areas, but current ramp, parking, road, water-entry, and flood conditions must be confirmed on launch day.
  • The two named campsites are not promised boat landings or drive-to bailouts; do not cross private banks or canal structures to shorten the route.
  • The Hancock gauge is direct same-river evidence but cannot certify local depth, wind, debris, dam hydraulics, portage conditions, or the Big Slackwater landing.

Watch for

  • USGS 01613000 Hancock stage, discharge, and trend
  • American Whitewater 2.785 ft low-runnable boundary, falling/rising trend, wind, cold water, floating wood, strainers, private banks, and flooded access
  • Williamsport power-plant dam, confirmed portage, Cumberland Valley/Opequon camping context, Big Slackwater ramp/parking, and the hard Dam 4 boundary

Route gallery

See this route on the water

Photos help show what the access looks like and what the route actually feels like on the water.

The historic Town Creek Aqueduct crosses the C&O Canal corridor beside the Potomac River in Maryland.
C&O Canal and Potomac River corridor at Town CreekPhoto by Wikimedia Commons
Wikimedia Commons: public domain

Score & sources

Why this score

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Read quality
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Why this scoreToday's evidence strength is checking

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Why
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Data behind the scoreGauge, thresholds, and timing

These are the live readings and threshold notes behind today's score.

Gauge sitePotomac River at Point of Rocks, MD
Gauge heightChecking
DischargeChecking
24h trendChecking
24h changeChecking
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Rain last 24hChecking
Rain last 72hChecking
Air tempChecking
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Rain timingChecking
Ideal rangeNeeds paddler reports
Known low-water floor2.79 ft
High thresholdNot calibrated yet
Evidence strength behind the rangeOfficial data source
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Paddle Today updatedChecking
Main source behind this scoreNWS/MARFC Point of Rocks boating stages and C&O/NPS moving-water access guidance
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NotesWhat to know before you go

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

  • Named moving-water corridorWilliamsport to Dam 4, approximately 14.4 miles, Class I

    American Whitewater names the reach, exact route endpoints, two along-route C&O campsites, mandatory power-plant portage, Dam 4 boundary, and route-specific 2.785 ft low-runnable correlation.

    Source

  • Authoritative public accessWilliamsport River Bottom Park and Big Slackwater public C&O/NPS boat ramps

    The C&O Canal Trust and Maryland public-water-access record document the named public ramps and parking context; preserve near-water coordinates and verify current entry conditions.

    Source

  • Direct flow evidenceUSGS 01613000 Potomac River at Hancock, with 2.785 ft route-specific low-runnable context

    The USGS station is on the same river and American Whitewater supplies the route correlation; neither replaces visual inspection or dam/portage scouting.

    Source

  • Dam boundariesMandatory Williamsport power-plant portage and hard Big Slackwater take-out above Dam 4

    NPS identifies the power-company dam and Dam 4 as whitewater hazards; never run either structure or continue past the named take-out.

    Source

  • Camping postureCumberland Valley and Opequon Junction hiker-biker camping; no riverbank camping

    American Whitewater identifies the along-route camping sequence; current NPS conditions and vehicle logistics must be confirmed separately.

    Source

  • Live gaugeUSGS 01638500, Potomac River at Point of Rocks, MD

    This is a direct same-river station. Readings are provisional and must be combined with trend and visual conditions.

    Source

  • Approved route imageryRights-cleared public-agency or public-domain corridor image

    Wikimedia Commons public-domain C&O/Potomac corridor image used as route context; it does not certify current flow, ramp, weather, dam, or take-out conditions.

    Source

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Keep exploring

More routes to check next

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More in Maryland

All 140 routes
Maryland route guideBrowse every tracked Maryland route.Montgomery, Frederick, and Washington Counties / Central MarylandJump to routes in this region.

More on Potomac River

All 15
Big Pool / Fort Frederick Campground to Williamsport River Bottom ParkWashington County / Western MarylandModerate · Approximately 16.7 river miles, American Whitewater Potomac reach 0.4Big Slackwater Boat Ramp to Taylors Landing Boat Ramp with Dam 4 portageMontgomery, Frederick, and Washington Counties / Central MarylandAdvanced · Approximately 3.4 river miles downstream from C&O Canal mile 85.5 to mile 80.9, with a mandatory Dam 4 portageBond's Landing to Fifteen Mile Creek Boat Ramp / Little OrleansAllegany County / Western MarylandEasy · Approximately 9 river miles, Maryland DNR Green Ridge State Forest Bond’s Landing to Fifteen Mile Creek legBrunswick Boat Ramp to Point of Rocks Boat RampMontgomery, Frederick, and Washington Counties / Central MarylandModerate · Approximately 6.8 river miles downstream from C&O Canal mile 55.0 to mile 48.2

Nearby routes by distance

Conococheague CreekKemps Mill Park to Williamsport River Bottom Park · about 2 mi awayEasy · Approximately 4.5 miles from Kemps Mill Park to Williamsport River Bottom ParkAntietam CreekDevil’s Backbone Park to MD 34 / Porterstown Bridge · about 8 mi awayModerate · Approximately 7.9 Antietam Creek miles from Devil’s Backbone Park to MD 34Antietam CreekMD 34 / Porterstown Bridge to Antietam Creek C&O Campground and Potomac confluence · about 11 mi awayModerate · Approximately 5.8 river miles, American Whitewater Lower Antietam/Burnside Bridge SectionCatoctin CreekDoub's Meadow Park to Catoctin Creek Park & Nature Center · about 16 mi awayModerate · Approximately 16.2 river miles from Doub’s Meadow Park to Catoctin Creek Park & Nature Center

Quick answers

Potomac River paddling FAQ

What water level is good for paddling Potomac River?

Paddle Today watches Potomac River at Point of Rocks, MD and uses 2.79 ft as the conservative low-water floor for this route. The ideal range still needs more paddler reports.

Where does this Potomac River route start and end?

This route starts at Williamsport River Bottom Park / Potomac Park boat ramp and ends at Big Slackwater Boat Ramp above Dam 4, about Approximately 14.4 Potomac river miles from Williamsport to Big Slackwater above Dam 4 on the water.

Is this Potomac River route good for beginners?

This is listed as a moderate route. Expect more planning than an easy float, and use the live score, route notes, and source links before committing.

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