While there is no common point the Susquehanna, Delaware, and Schuylkill River drainage basins are very close to each other in the Honey Brook Basin, which is located between Welsh Mountain and the Baron Hills. Pequea Creek originates in the Honey Brook Basin and after flowing in a southeast direction turns to flow in a west and southwest direction to join the Susquehanna River. The West and East Branches of Brandywine Creek both originate in the Honey Brook Basin and flow along completely different routes before eventually converging to form southeast oriented Brandywine Creek, which flows to the Delaware River. And the South Branch French Creek originates in the Honey Brook Basin and flows in a northeast direction to join southeast oriented French Creek, which then flows to the Schuylkill River. Why is Honey Brook Basin a significant drainage divide area when higher uplands surround it?
Figure 1: The Honey Brook Basin as defined here is located between Welsh Mountain (5) and the Baron Hills (6) and is drained in the west by Pequea Creek (4) to the Susquehanna River, in the center and southeast by the West (3) and East (2) Branches of Brandywine Creek to the Delaware River, and in the northeast by the south branch French Creek (1) to the Schuylkill River. United States Geological Survey map digitally presented using National Geographic TOPO software.
Figure 1 illustrates the Honey Brook basin area between Welsh Mountain (number 5) and the Baron Hills (number 6). The town of Honey Brook is located near the figure 1 center. The Conestoga River originates north of Welsh Mountain and can be seen flowing in west-southwest direction across the figure 1 northwest corner. West of figure 1 the Conestoga River flows in a west, south, and southwest direction to join the Susquehanna River. The South Branch French Creek (number 1) originates and flows in a northeast and east direction to the figure 1 northeast corner. East of figure 1 the South Branch French Creek flows in an east and northeast direction to join southeast and east oriented French Creek, which flows to join the southeast oriented Schuylkill River at Phoenixville.
The East Branch of Brandywine Creek (numbers 2) originates in the two lakes (reservoirs) with separate diverging headwaters streams that then converge and flow in an east direction to the figure 1 east edge. East of figure 1 East Branch Brandywine Creek flows in a southeast and south direction to cross the Chester Valley and then in a south-southeast direction to join West Branch Brandywine Creek and to form south and southeast oriented Brandywine Creek. The West Branch Brandywine Creek (numbers 3) flows from north and west of Honey Brook to a water gap at the Baron Hills east end and south of figure 1 flows in a southwest and south direction to cross the Chester Valley and then in a southeast direction with some northeast jogs to eventually join the East Branch Brandywine Creek and to form Brandywine Creek, which flows to the Delaware River.
Elevations along the Welsh Mountain crest exceed 900 feet and in places exceed 1000 feet while some Baron Hills crest elevations exceed 800 feet and in places exceed 900 feet. The drainage divide between South Branch French Creek headwaters and East Branch Brandywine Creek headwaters has an elevation of between 640 and 660 feet at two separate points. The lowest point on the drainage divide between East Brandywine Creek and West Branch Brandywine Creek in the Honey Brook basin region has an elevation of approximately 660 feet. The lowest point on the drainage divide between West Branch Brandywine Creek and Pequea Creek is between 700 and 720 feet. In other words, all drainage divides have similar elevations, although the drainage divide elevations increase in progression from east to west.
The low drainage divides between Welsh Mountain and the Baron Hills which link the Schuylkill River (South Branch French Creek), the Delaware River (East and West Branches Brandywine Creek), and the Susquehanna River (Pequea Creek) were all crossed by massive and prolonged southwest oriented floodwaters moving from north and east of the present day Schuylkill River valley to what at one time was the actively eroding Susquehanna River valley. Headward erosion of the actively eroding southwest oriented Pequea Creek drainage basin across what is today the southern half of the Conestoga Valley first lowered the area between Welsh Mountain and the Baron Hills.
Headward erosion of the south oriented West Branch Brandywine Creek valley captured the southwest oriented floodwaters and diverted flood flow from what had been the actively eroding Pequea Creek drainage basin and Susquehanna River valley to the actively eroding Brandywine Creek drainage basin and to what at that time was a newly eroded Delaware River valley. Headward erosion of the south oriented West Branch Brandywine Creek valley captured the southwest oriented flood flow first and probably ended flood flow to the Pequea Creek drainage basin. East Branch Brandywine Creek valley headward erosion, which occurred at approximately the same time as the West Branch Brandywine Creek headward erosion, captured the southwest oriented floodwaters next ended flow to the newly eroded West Branch Brandywine Creek valley.
Shortly thereafter (in terms of regional erosion) headward erosion of the southeast oriented French Creek valley (from the actively eroding Schuylkill River valley) beheaded and reversed the southwest oriented flood flow moving into the Honey Brook Basin area and created the present day east and northeast oriented South Branch French Creek drainage route. Reversal of flood flow in the present day South Branch French Creek valley ended flood flow to the actively eroding East Branch Brandywine Creek drainage basin and to the Honey Brook Basin, although for a time southwest oriented floodwaters continued to erode the Conestoga River drainage basin north of Welsh Mountain, although Schuylkill River valley headward erosion ended that flow as well.