Living Near Stevens Run and Rock Creek: Flood Maps, Storm Water and Mold

By John Calhoun, owner of Mold Remediation Gettysburg PA · Updated October 20, 2026

Two creeks shape the low ground in Gettysburg. Stevens Run starts south of town, crosses the battlefield and runs through the borough before it empties into Rock Creek, which follows the east edge of town. If you live near either one, here’s what’s documented, what isn’t, and what I’d do about your basement.

What’s documented about the two creeks

Stevens Run is named for Thaddeus Stevens and has gone by Stevens Creek and the Tiber. Inside the borough it runs in a concrete channel, including a covered section. Colt Park drains toward it.

Rock Creek is about 19 miles long and drains roughly 65 square miles before it reaches the Monocacy River. Its recorded history includes a flood that swept away a bridge in 1841, one that destroyed a mill dam around 1870, and a 1923 flood that broke a temporary bridge.

The flood maps. The borough’s floodplain ordinance, adopted in 2020, uses FEMA’s flood insurance study and flood maps dated July 22, 2020. Those maps show flood zones and floodways for the borough.

What I haven’t found is a reliable source saying which streets or houses take water in a storm today. So I won’t tell you that your block floods, and you shouldn’t believe anyone who says so without showing you the map. Look up your own address on the FEMA Flood Map Service Center.

The flood record, by the numbers

FEMA’s flood insurance records give a real picture of how often water has turned into claims around here, without pretending to say which houses get wet.

The 17325 ZIP code reaches well beyond the borough, so don’t read the claim count as a borough number. Adams County has also had federal disaster declarations for flooding or tropical storms in 1972 (Agnes), 1975, 1976, twice in 1996, 2004, 2006, 2011 (Lee) and 2012 (Sandy). The full table is on the Gettysburg housing data page.

Two things stand out. Big claim years come from a handful of big storms, several of them the remnants of tropical systems. And very few properties carry flood insurance: 27 active policies in a borough of about 2,800 homes. Most homeowners policies don’t cover flood, so if you’re close to either creek, it’s worth a conversation with your agent before the next big storm.

The borough’s channel wall project

The Gettysburg Borough Stormwater Authority has been working on the concrete walls along Stevens Run. Minutes from June 2025 rank wall repairs between Gilliand Alley and Carlisle Street as the first priority, with walls behind Gettysburg Glass on Water Street next. Draft minutes from February 2026 describe a larger Stevens Run wall replacement project with an estimated total of six to ten million dollars and four priority areas: Carlisle Street, East Water Street, West Middle Street and an alley wall behind Dollar General.

That’s public planning, and it tells you the borough takes the channel seriously. It doesn’t tell you anything about the condition of your basement. For that, someone has to look.

Is it the creek, or is it the house?

A wet basement near a creek isn’t automatically the creek’s fault. Water from the roof, a clogged gutter, a downspout dumping against the foundation or soil sloping toward the house is a common cause anywhere, and it’s the first thing I check. Heavy rain fills the soil around a foundation whether there’s a creek nearby or not. On NOAA’s normals, June and September are Gettysburg’s wettest months.

The way to tell is to follow the water. Where does it come in, at the wall, the floor crack or the floor drain? When, during the rain or a day after? Moisture readings around the room, taken the right way, sort that out. Basement mold in Gettysburg homes walks through it.

After a storm puts water in the basement

1. Stay safe first. Don’t walk into standing water near outlets or appliances. If the power has to go off and you’d have to stand in water to reach the panel, call an electrician.
2. Photograph everything before you clean, for insurance.
3. Get the water out and start drying the same day. The EPA says to dry water-damaged materials within 24 to 48 hours to prevent mold.
4. Treat creek water as dirty water. IICRC guidance puts rising water from rivers and streams in the most contaminated category, with sewage. Porous things it soaked usually go. Sorting what stays is in what to throw away after mold.
5. Check the sump pump if you have one. If it quit, start with the sump pump quit.

A low-ground habit worth keeping

Look at the basement after every big rain, not just when it smells. Five minutes with a flashlight beats five days of drying. If you want a second set of eyes, I’m John Calhoun, and that’s what I do. The borough’s housing and rain numbers are on the Gettysburg housing data page, and the overview of mold remediation in Gettysburg, PA and my mold services cover the rest.