Wednesday, June 22, 2022

Tropical Storm Agnes - Focus on the Forks of the Delaware

We are continuing our series examining the impact of Tropical Storm Agnes as it blanketed regions of Pennsylvania with heavy rainfall in June of 1972. This week’s blog focuses on the area of eastern Pennsylvania sometimes referred to as the Forks of the Delaware. From grade school days we all hopefully remember that the Delaware River is what gives the distinctive shape to Pennsylvania’s eastern border with neighboring New Jersey. Flowing from the northwest, the Lehigh and Schuylkill rivers are the main tributaries, or “forks”, of the Delaware River. The Lackawaxen River, flowing through Wayne and Pike counties could conceivably be considered a third (and northernmost) major fork of the Delaware. 

Delaware River Basin– Image credit USACOE website

In George Donehoo’s book, A History of the Indian Villages and Place Names in Pennsylvania, he notes that the name Lehigh is an English corruption of a German abbreviation (Lecha) of the Delaware word Lechauwekink, meaning “at the forks” or “where there are forks” (pg. 89).

The headwaters of the Lehigh River originate in the Glaciated Pocono Plateau Section of the Appalachian Plateaus Physiographic Province. This area roughly corresponds with what early maps identify as the “Great Swamp”. Today we recognize this area as one of Pennsylvania’s outdoor vacation hotspots, the Poconos. Much like the Schuylkill does just above Hamburg, the Leigh works its way from the north through the Kittatinny Ridge below the town of Palmerton.

Great Swamp – detail of map from Wallace’s Indian Paths of Pennsylvania

From the Lehigh Gap south, the river serves as the boundary between Lehigh and Northampton Counties until the borough of Catasauqua. Also similar to the Schuylkill, the Lehigh’s course shifts from south to east when its waters encounter the South Mountain, a topographic feature that corresponds with Reading Prong Section of the New England Physiographic Province. From the county seat Allentown, the Lehigh flows east through Bethlehem and empties into the Delaware at Easton.

The Francis E. Walter Dam, near White Haven, was built in 1961 by the US Army Corps of Engineers and works in conjunction with the later constructed Beltzville Dam as multi-tiered flood control system for the Lehigh River. According to the Army Corps’ website, it is accredited with preventing 233 million dollars’ worth of flood damage, presumably the lion’s share of that estimate made up from property downstream that was spared the wrath of Agnes. The success of the dam in mitigating severe flooding further downstream is also evident in the historical crest data available on NOAA’s website. As measured at Bethlehem, the top three floods occurred in 1902, 1942 and 1955, respectively, and at #4 (and more than 3 feet lower than #3) the 1972 Agnes event.

Constructed prior to the National Historic Preservation Act of 1966, the F.E. Walter Dam and reservoir did not initially benefit from a systematic archaeological survey. Later modifications to the dam did however trigger archaeological surveys in the 1980s. At last count nearly two dozen prehistoric sites have been identified around the F.E. Walter Dam project area representing all time periods from Paleo through the Late Woodland. Nearly four dozen historic sites were also identified, many relating to the lumber industry that was prevalent in the area during the mid-19th century.

Projectile points from the Tobyhanna Flats site (36Cr37)

Artifacts collected from the Tobyhanna Flats site, 36Cr37, located at the confluence of the Tobyhanna Creek and Lehigh River, are typical of many of the sites that were identified during the project to make modifications to the F.E. Walter Dam. Relatively low densities of lithic debitage comingled with historic architectural debris and mid-19th through the early 20th century domestic ceramics, iron spikes and other miscellaneous hardware fragments were found to be common occurrences. Some objects of note from 36Cr37 include the projectile points seen above, indicative of the Archaic and Woodland time periods. With a patent date of 1911 legible on the reverse, this mid-20th century brass Boy Scout insignia pin (also recovered from 36Cr37) consists of a familiar eagle with a stars and stripes shield or crest, flanked by two stars imposed over a fleur-de-li symbol, and is associated with a scout achieving the rank of Tenderfoot.

Boy Scout Insignia pin from Tobyhanna Flats site (36Cr37)

Shifting our focus slightly to the west, the tributaries of the Schuylkill begin their journey towards the Delaware Bay in the Upland Anthracite Section of the Ridge and Valley Physiographic Province that encompasses the central portion (roughly half) of Schuylkill County. The eastern boundary of the Schuylkill watershed includes tributaries draining portions of western Lehigh and Bucks counties, while the western edge of the Schuylkill watershed, extending into the eastern corner of Lebanon County, represents the boundary between water flowing west into the Susquehanna and ultimately the Chesapeake Bay, and water making its way east draining into the Delaware Bay.

Flowing south through the Kittatinny Ridge, or Blue Mountain as it is alternately referred, the Schuylkill tracts southeast at the Berks County seat of Reading. Continuing along its course, the Schuylkill serves partly as the boundary between Chester and Montgomery Counties as it meanders past towns like Pottstown, Phoenixville, and Conshohocken. PA route 422 roughly parallels the Schuylkill from Reading to King of Prussia, and the Schuylkill then finally meets the Delaware River in a heavily industrialized south Philadelphia, between the international airport and the Philadelphia Navy Yard.

For the Schuylkill, the Agnes flood is still considered the worst natural disaster in Berks County. NOAA’s flood records as measured at Reading corroborate these sentiments with the 1972 crest holding the top spot at 31.3 feet, with the second highest crest a distant 7.5 feet lower. The reader is directed to the website Berk’s County Nostalgia, which has done an excellent job of compiling contemporary newspaper clippings and photographs that capture the magnitude of the flooding in Reading and the surrounding area.

Unfortunately, work to build a dam across the Tulpehocken, the Schuylkill’s westernmost tributary, that would impound the waters to become Blue Marsh Lake, would not begin until 1974. However, a systematic archaeological survey was able to be conducted in 1976, with over two dozen sites being identified through controlled surface collection and shovel testing, six of which were recommended as being eligible for inclusion to the National Register of Historic Places for their potential to yield new and important information about the prehistory of the region.

 A short article written by Ron Devlin in 2013 for the Reading Eagle entitled The Land down under at Blue Marsh Lake focuses on the impact on the residents who were displaced from their farmsteads and homes to make way for the new lake. Much history was lost, but the preservation minded community was successful in having the Gruber Wagon Works building moved to higher ground. A National Historic Landmark, now restored and with guided tours available, this late 19th – early 20th century wagon workshop today sits on the grounds of the Berks County Heritage Center. This unique structure is also featured in The State Museum of Pennsylvania’s gallery of Anthropology and Archaeology.

Gruber Wagon Works exhibit panel, State Museum of Pennsylvania Anthropology and Archaeology gallery

We hope you’ve enjoyed this brief overview of the Schuylkill and Lehigh Rivers, the impacts of Agnes, and preservation efforts connected to major flood control projects for these tributaries of the Delaware River in Pennsylvania. Be sure to catch the next blog as we look at flooding in the central region of the Susquehanna River valley.  Please join us on June 24th, 2022 for  Learn at Lunchtime with Curator, Janet Johnson as she discusses the impact of Agnes on the cultural resources of the Commonwealth and highlights some of the archaeological sites explored in this blog series. 



Donehoo, George P.

A History of Indian Villages and Place Names in Pennyslvania

Wennawoods Publishing Lewisburg, PA (1999)


Kinsey III, W. Fred

Archaeological Survey and Evaluation of Blue Marsh Lake, Pennsylvania

North Museum Publication No. 3, Franklin and Marshall College (1976)


Wallace, Paul A. W.

Indian Paths of Pennsylvania

Pennsylvania Historical and Museum Commission, Harrisburg (1971 second printing)


Army Corps of Engineers websites:

Berks County Heritage Center website:

Berks Nostalgia website:

NOAA flood data websites:



For more information, visit or the Hall of Anthropology and Archaeology at The State Museum of Pennsylvania .