The Conestoga is not only impacted by its watershed area but also by the waterway into which it flows. Conversely, the Susquehanna River is only slightly influenced by the Conestoga. By way of comparison, the Susquehanna drains 56 times the area of the Conestoga and travels seven times the distance on its way to the Chesapeake Bay.
The Susquehanna River may be ranked only as the 16th longest river in the world, but it’s considered to be among the very oldest rivers in the world. Its history is larger in scope than the Conestoga, but the Susquehanna has seen many of the same trends and human impacts. Geology always sets the stage in any landscape. So it does for the interface between these two rivers. Some geologists have opined that for several eons, it actually flowed from south to north. Its age can be seen by the multitude of cuts that the Susquehanna has made through various ancient mountain ranges.
Another under-recognized geologic feature at the mouth of the Conestoga is the cut made through a ridge that parallels the Susquehanna. It’s rather dramatic, once noticed. Imagine what an enormous lake must have existed for millions of years stacked up behind this ridge, as the watersheds attempted to drain into the Susquehanna. Along with other streams that drain our County, the Conestoga dissolved, eroded, and chipped away at this ridge to flow freely.
One of the earliest photographs of the mouth of the Conestoga was taken after two railroad bridges had already been built.
Here’s a contemporary view from a similar point in the Susquehanna.
An illustration of even earlier days is of the Slackwater Navigation. One of the pleasure-craft “packet boats” is depicted approaching Lock #9. Aside from the mule team, there’s also a trumpeter on the bow, signaling the vessel’s approach to the lock.
This boat might have been traveling from either upstream or downstream along the Susquehanna since there had been a dam and boat channel installed across so that folks from Lancaster could make their way down to Baltimore or up to the Juniata & points west.
The Safe Harbor Dam has dramatically changed the landscape of both rivers. But the view at the mouth of the Conestoga is far less bucolic.
When the Susquehanna rises, the Conestoga can’t drain. It’s simple enough to comprehend that rainstorms in New York might not ever darken the skies in Lancaster County. Yet, if those storms are large enough and intense enough, then the Conestoga will be impacted by a flooding Susquehanna. We don’t experience that at all in our memories, mostly due to the Safe Harbor Dam. It’s directly upstream of the mouth of the Conestoga.
This brings to mind a funny story. Don Kautz and I were happily mucking about at the site of Lock #9 of the Conestoga slackwater navigation system, photographing features around us and trying to orient ourselves to a newly deployed map from 1853 that depicted Safe Harbor Village. We heard a public address system alerting anyone nearby of a dam discharge release. Sure enough, the Conestoga appeared to be flowing backwards with a little 6” tidal wave.
Not so funny was a storm in 1972. Hurricane Agnes made its way up the eastern US from mid-June into early July. It severely flooded the Susquehanna and many communities in Pennsylvania. Much of the state experienced more than 7” of rainfall, with a large swath in the central part of the state reporting more than 10”. Peak rainfall was 19” in western parts of Schuylkill County. But the sheer size tipped the scales, as there was nowhere for the water to go. That June had already been soggy here. Everything was inundated.
More than 100,000 Pennsylvanians were forced to leave their homes. Some buildings in Harrisburg were under 13’ of water. Similar impacts were felt in neighboring states. As a result, FEMA and the US Army Corps of Engineers began a much more rigorous mapping and regulation of floodplains. The beginning of stormwater management regulations was prompted.
The 1972 flooding by Agnes caused quite a surcharge at the mouth of the Conestoga. So, for days after the rain stopped here, the floodwaters only slowly ebbed.
As written elsewhere here at Uncharted Lancaster, the village of Safe Harbor was ravaged multiple times by floodwaters’ more powerful wintertime cohort in destruction, ice jams. Freezing temperatures stack up solid water that will inevitably melt. With changing water volumes and sometimes erratic temperatures, an early thaw can cause the ice to “flow” as a semi-solid mass reaching incredible heights of great weight and force. These ice jams would flow up the Conestoga just like the little 6” tidal wave Don and I observed.