Carroll County's northwest border is different rock from the rest of the county. The plan describes Ridge and Valley ground there, parallel valleys and ridges running roughly northeast to southwest, with several of those ridges forming the county's northwest border, and it says that in the northwestern portion of the county the New River crosses folded and faulted dolomite, limestone and shale formations.
The plan says groundwater recharge capability in that area is not known, "but conditions seem to be favorable for obtaining large quantities of groundwater at properly located sites." Everywhere else, the plan says, igneous and metamorphic rocks underlie Carroll County, and for that rock it gives 20 to 100 gallons per minute as the range of estimated potential well yield, a figure for planning rather than a test of any one well. What yield means for a single well is under well yield. Where a county main runs instead, the question moves to the public water systems the Public Service Authority operates.
In Carroll County the plan gives the New River a gradient of 14 feet per mile and a width of 300 to 800 feet, with numerous rapids and shallows. It names two dams on the river inside the county, Byllesby at 54 feet high and Buck at 32 feet high, both owned and operated by the Appalachian Power Company, and USGS lists a monitoring location named for each dam. Whether a given stretch of New River frontage floods is a separate, parcel-level question.
The plan names two other high points, both away from Fisher Peak. Chestnut Knob, west of the New River, rises to 3,374 feet, and Bear Knob, in the northeast corner of the county near the Pulaski County line, reaches 3,390 feet.