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

Potomac RiverWilliamsport River Bottom Park to Big Slackwater Boat Ramp above Dam 4

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.

Route location

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Plan this route

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

Need to know

Why this call
This route is documented for planning, but does not receive a Paddle Today score.
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Route overview

Trip details

Access rules, camping, seasonal conditions and trip length.

Distance, difficulty, rules and camping
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

Tomorrow and the weekend

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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.

Access map

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Start

Put-in

Williamsport River Bottom Park / Potomac Park boat ramp
Open mapDirections to put-in

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
Open mapDirections to take-out

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.

Road shuttle

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Access notes and hazards

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

Plan this paddle

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Conditions

Water levels, gauge history, and hourly forecast

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Gauge detail

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Gauge

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Route gallery

Photos

Check each caption: some photos show the surrounding area rather than this exact trip.

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

Sources

Data and sources

Read the access and hazard notes and check the linked guides. We do not issue a daily score for this trip.

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

Compare another stretch on this river, or explore different rivers within 75 straight-line miles.

More in Maryland

All 131 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 14
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 MarylandHard · 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 within 75 miles

Conococheague CreekKemps Mill Park to Williamsport River Bottom Park · about 2 straight-line 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 straight-line 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 straight-line 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 straight-line 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 best for the Williamsport River Bottom Park to Big Slackwater Boat Ramp above Dam 4 route on the Potomac River?

This planning route has no live Paddle Today score. Review the linked water-level sources, current access notices and route-specific hazards before travel.

Where does the Williamsport River Bottom Park to Big Slackwater Boat Ramp above Dam 4 route on the Potomac River 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, Approximately 14.4 Potomac river miles from Williamsport to Big Slackwater above Dam 4 on the water.

Is the Williamsport River Bottom Park to Big Slackwater Boat Ramp above Dam 4 route on the Potomac River suitable for beginners?

This is listed as a moderate route. Review the difficulty notes, hazards and current access conditions against your group's skills. No live score assesses this trip.

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