Freestone · Mixed Sedimentary · New Jersey, US

Big Flat Brook

A rustic wooden suspension bridge crossing Big Flat Brook, surrounded by lush green woodland, Sussex County, New Jersey.

The Big Flat Brook is the jewel of New Jersey trout water — a clear freestone running down through the Delaware Water Gap country in Sussex County, with the Blewett Tract set aside as fly-fishing-only and managed for a quality experience.

Today · About as good as it gets
Sculpin Streamer
Forecast · Today
About as good as it gets
On the feed top to bottom — start on the rises with a dry, drop a nymph if they stay down.
90% projected
Today's fly
Sculpin Streamer
Sculpin Streamer
Conditions on the water · Today
Live gauge
Level
Steady
0.64 m
Water temp10.9°C
ClarityClear
Weather8°C
WindN 20 km/h
Pressure1020 hPa
Rain · recent6.6 mm
Rain · ahead0.0 mm

The nearest gauge doesn't record temperatures, so we've estimated it — defer to the river keeper's advice.

Water temperature for Brown Trout
Ideal
11°C est.ideal 10–16°C
0°14°28°
How to fish it · for Brown Trout
When
Nymphing can work through most of the day.
Where
Cover mixed depths.
Method
Start with tight-line nymphs and adjust if fish rise or drift higher.
Kit
9 ft #4 rod, floating line, 12 ft tapered leader to 4–5 lb fluoro tippet.
Why this works
Excellent — water temperature is right today, though time of day could be better.
Likely species
Mayflies
Chironomids
Gammarids
Hatch timeline · todayPeak at 9pm

12pm(now) — Eastern Blue-Winged Olive

Stage: On emergersApproach: Emerger or dryActivity: 63%
Also:Black Midge31%
Peak emergence window5 food groups active

Peak activity at 9pm — Brown Dun (Brown Dun, 4 food groups active)

Sub-surface · on the nymphunder the surface

Hatch predictions

Supporters see the full sub-surface read.

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Beyond the hatch · worth watchingambient prey(1)

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Evidence
Records-basedModerate confidence

Based on species-occurrence records, not local invertebrate surveys.

Through the year
0–3 scale · October highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
1
2
2
2
2
2
2
2
2
2
2
1
Brown DunHatch
2
3
3
3
3
3
3
2
Quill GordonHatch
2
2
Blue QuillHatch
2
3
2
HendricksonHatch
2
2

Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.

Ranked for today
Brown Trout fly box
Permits & access
Permit required — see local rules.
  • New Jersey licence and trout stamp required; fly-fishing-only on the Blewett Tract with delayed-harvest-style special regulations — verify current NJDEP Fish & Wildlife rules and seasonal windows before you fish.
What's coming
Plan ahead
5-day outlook
Other water nearby · 2
Musconetcong River
49 km
84
Brown trout · Rainbow trout
Ramapo River — New York
56 km
0
Brown trout · Rainbow trout · Brook trout
Gallery · 2
  1. A rustic wooden suspension bridge crossing Big Flat Brook, surrounded by lush green woodland, Sussex County, New Jersey.
    Shaky
  2. Terrain map of the venue
    Terrain map
About this water

The Big Flat Brook is the jewel of New Jersey trout water — a clear freestone running down through the Delaware Water Gap country in Sussex County, with the Blewett Tract set aside as fly-fishing-only and managed for a quality experience. It holds stocked browns and rainbows and a scattering of wild fish, with proper hatches and the kind of pretty pocket-and-pool water that makes you forget you're an hour from the New York line. It's a true freestone, so it runs cold and full in spring and thins and warms by midsummer; fish it in the good water of spring and fall and tread lightly through the catch-and-release stretch.

  • Mixed sedimentary
Water quality · US Clean Water Act
  • Aquatic life: Impaired
  • Recreation: Impaired
What this classification means

Recreation: Bacteria/pathogen advisory — mind wading cuts and immersion.

EPA ATTAINS assessment unit 'Flat Brook (Tillman Brook to Confluence)' (NJ02040104150010-01), 2022 Integrated Report. Aquatic Life use: Not Supporting. Listed impairment causes: Temperature, Metals Other Than Mercury, Pathogens. This is a Clean Water Act assessment-unit classification (the US analogue of WFD), not a live reading.

Status is for the Clean Water Act assessment unit covering this reach.

EPA ATTAINS (Clean Water Act) · NJ02040104150010-01

The full read · show the working · for Brown Trout · confidence 90%
How the 84 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time55 × 13%7.2
Pressure80 × 7%5.6
Insect activity68 × 12%8.2
Conditions total= 84
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
What would change the calculation
The dawn and dusk windows score higher than the midday lull.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout 1 January → 31 December
Related guides
Euro Nymphingsubsurface methods
Casting instructors near here
Booking & contacts