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.

Tomorrow · A proper day on the water
Trico Spinner
Forecast · Tomorrow
A proper day on the water
A proper day for it. Work the seams with an upstream nymph, switch to the dry when they show.
75% projected
Today's fly
Trico Spinner
Trico Spinner
Conditions on the water · Tomorrow
Live gauge
Level
Steady
0.61 m
Water temp16.8°C
ClarityClear
Weather22°C
WindN 14 km/h
Pressure1016 hPa
Rain · recent4.4 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
Warm — slow
17°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
Water at 19.2°C — above the brown trout caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots.
Likely species
Mayflies
Caddisflies
terrestrials
Hatch timeline · tomorrowPeak at 7am

12pm(now) — Reed Smut

Stage: On emergersApproach: Emerger or dryActivity: 74%
Also:Trico (Eastern)46%Flying Ants45%
Peak emergence window4 food groups active

Peak activity at 7am — Trico (Eastern) (Trico (Eastern), Degree-days at peak)

Sub-surface · on the nymphunder the surface

Hatch predictions

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Beyond the hatch · worth watchingambient prey(1)

Hatch predictions

Top prey shown — see all 2 with Pro.

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Evidence
Records-basedModerate confidence

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

Through the year
0–3 scale · September 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
Water here around 19°C. Nothing cooler within range — carry a thermometer.
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 80%
How the 33 is built — score × weight = contribution
Temperature22 × 28%6.2
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time85 × 13%11.1
Pressure80 × 7%5.6
Insect activity66 × 12%7.9
Limiting factor: Water temperature (19.2°C) is outside Brown Trout's preferred range (10–16°C)= 66
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
What would change the calculation
Cooler water — back toward the 10–16 °C ideal band — would lift the score and ease welfare.
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout 1 January → 31 December
Related guides
Euro Nymphingsubsurface methods
Casting instructors near here
Booking & contacts