Floodplains are primarily located along the shores of the Potomac and ShenandoahRivers, sometimes reaching inland along stream banks that drain into these rivers. Many forests on the lower floodplain are dominated by silver maple (Acer saccharinum), sycamore (Platanus occidentalis), and green ash (Fraxinus pennsylvanica). Upper floodplains are commonly covered with tulip poplar (Liriodendron tulipifera), sugar maple (Acer saccharum), hackberry (Celtis occidentalis), and white ash (Fraxinus americana). During a recent vegetation inventory, Shumard oak (Quercus shumardii) was recorded for the first time in the park along the banks of the Potomac. This tree is one of the largest oaks, preferring moist, well-drained, bottomland soils on stream and river banks.