The Watershed Atlas  ·  No. 01 — Lower Eighteenmile  ·  No. 02 — Hunnicutt  ·  No. 03 — Berkeley

Clemson  ·  Flashy — next in line

The Watershed Atlas · No. 03

Berkeley Creek

A small headwater tributary of Eighteenmile Creek on Clemson’s east side — the “Berkeley Orchard” reach, where a capstone crew hand-taped ten cross-sections in the channel. Barely two miles of stream, and one of the fastest-developing little watersheds in the area.

2.8 sq mitributary of Eighteenmile Creek1.9 mi of channel94% one soil group
Terrain and stream map of Berkeley Creek
Terrain & streams · USGS 3DEP 1 m LiDAR hillshade + NHD flowlines. The creek falls about 86 ft to its confluence with Eighteenmile Creek.

The ground

A fast-building headwater

Berkeley Creek drains 2.8 square miles of the Eighteenmile basin — old orchard, new subdivisions, and the ground filling in between. Like the rest of the Piedmont here, it is almost entirely group-B clay: 94% of the watershed drinks water at the same rate.

What sets it apart is the pace. This is a headwater — the top of the system — and it is building out faster than almost anywhere upstream of it.

85%
Developed land, 2023 — up from 69% in 1985
21%
Impervious surface, 2023 — past the 10% line
94%
Soils in hydrologic group B

What's changing

Already past the first line

Impervious cover climbed from about 14% of the watershed in 1985 to 21% in 2023. That matters because of where the thresholds sit: the Center for Watershed Protection’s model marks stream degradation beginning past 10% hardening and healthy aquatic life generally lost past 25%. Berkeley crossed the first line decades ago and is climbing steadily toward the second.

Impervious cover, 1985–2023

Share of the 1,801-acre watershed that is impervious, with the two Center for Watershed Protection thresholds. Source: USGS EROS Annual NLCD Fractional Impervious Surface, 30 m.
A headwater is the cheapest place to fix this.

Water here is still spread thin across the top of the watershed, before it concentrates into the channel. Slowing it now — in the orchard, the new lots, the roadside swales — costs a fraction of fixing the flood downstream. The stream-scale view of this reach, with the ten field-taped cross-sections, lives in Four Streams.

Land cover map
Land cover, 2023 · NLCD.
Impervious surface map
Impervious surface, 2023 · NLCD.

Where the green is

Orchard and forest, filling in

Developed land went from about 69% of the watershed in 1985 to 85% in 2023. Forest fell from 21% to 12%, and the old orchard/pasture from 10% to 3%. Set against its own parent watershed — Lower Eighteenmile, No. 01 — Berkeley is the harder-edged, faster-changing headwater.

Berkeley Creek

Land cover by area · 2023

Lower Eighteenmile · No. 01

Composition, not size · same year
2023

Water quality — the 303(d) list

What it drains into

Berkeley Creek is small enough that it isn't a separately monitored segment on the state's 303(d) list.

But it drains straight into Lower Eighteenmile Creek — which is listed, for turbidity, nutrients, and pathogens (bacteria) (with a cleanup plan on record). Whatever this watershed sheds, it sheds into an already-impaired water.

Source: EPA ATTAINS (the national clearinghouse for state Clean Water Act §303(d)/305(b) assessments), current reporting cycle. “Cause” = the pollutant; “use” = what it keeps the water from supporting (swimming, aquatic life).

What the water does now

Small, steep, and quick

The curve-number model puts the flashiness in numbers. Berkeley’s runoff curve number rose from about 67 to 69 as it hardened — and being small and steep, it responds fast:

Runoff volume per storm — 1985 vs 2023

Total runoff leaving the 1,801-acre watershed by storm size. Curve-number model calibrated to USGS StreamStats (RCN 68.8); storm depths from NOAA Atlas 14. Acre-foot ≈ 326,000 gallons.
The everyday 2-year storm now sheds about 22 acre-feet more than it did in 1985.

A 14% jump — about 7 million extra gallons from one ordinary rain, arriving faster and heading straight for Eighteenmile Creek. The 100-year storm sheds roughly 48 acre-feet more.

Why it matters downstream

This is where the impairment starts

Berkeley itself is too small to be its own line on the state’s impaired-waters list — but it is a headwater of a creek that is listed. Turbidity, nutrients, and bacteria don’t originate in the mainstem; they wash off the hardening headwaters and collect downstream. Fixing the big creek means fixing the little ones that feed it.

That is the good news, too: the leverage is highest right here, at the top, where the water is still easy to catch.

Slow it · spread it · sink it

The receipts

Every number, from open data

The watershed was delineated fresh from its Eighteenmile confluence using USGS SS-Delineate (2.81 sq mi, matching the atlas’s outlet drainage area); every figure is computed locally from public sources.

Watershed boundaryUSGS SS-Delineate v1, delineated from the Eighteenmile Creek confluence — 2.81 sq mi (the full tributary watershed).
Impervious & land coverUSGS EROS Annual NLCD Collection 1 — Fractional Impervious Surface and Land Cover, 30 m, 1985–2023.
Streams & terrainUSGS NHD flowlines; USGS 3DEP 1 m LiDAR hillshade.
Soils / hydrologic groupUSDA SSURGO via Soil Data Access — area-weighted.
Runoff modelTR-55 / SCS Curve Number, calibrated to USGS StreamStats basin characteristics (RCN 68.8).
ImpairmentsEPA ATTAINS §303(d)/305(b) assessment service, current cycle.