The floodplain appears to have been recently disturbed from overbank flow. The bed of the stream is bedrock, with outcrops of gneiss visible. Sand and gravel deposits are present along the banks. The water level on the upstream side of the culverts is slightly higher than downstream. The stream flows to the culverts at nearly a 45-degree angle and a portion of the stream bank runs almost parallel to the road.
Coarse gravel lines the streambed.
Sand and gravel is deposited on the lower banks and point bars. These deposits include quartz, some muscovite, biotite, gneiss and mica schist. Further upstream, the banks are higher and more eroded. Springs flow over this clay surface and discharge into the stream. No outcrops of gneiss were observed along this part of Horsepen Run.