THE HISTORICAL PHYSICAL BEHAVIOR OF THE LOWER SUSQUEHANNA RIVER, PENNSYLVANIA, 1801-1976

The channel of the lower Susquehanna River in southeastern Pennsylvania has changed in a variety of ways since Benjamin Henry Latrobe carried out his program of localized channel clearance and conducted his river survey in 1801. Using Latrobe's survey materials, including a 1:12,672 map as a base, this study examines physical change over a period of one hundred and seventy five years (1801-1976) in response to natural and culturally influenced processes. It describes and analyzes the formation and modification of alluvial islands and development of the floodplain in a 7.8 mi (12.5 km) reach of the river between Marietta and Turkey Hill, Lancaster County.;This waste, following a transport time of approximately 30 to 40 years, transformed the channel of the lower Susquehanna River by changing the composition of the material in transport and by reducing the width and depth of the channel through construction of elevated floodplains and expansion of alluvial islands. The completion of Safe Harbor Dam in 1931 and the formation of Lake Clarke Reservoir which inundated the lower half of the study area accelerated local deposition of anthracite coal waste.;Sediment yields have declined in the Susquehanna River basin since 1956 due to reduced anthracite coal production, adoption of improved mining technology, implementation of sediment control procedures, reforestation, and more conservation oriented farming. If this trend continues in the future the man-induced depositional trend of the last 130 years will be reversed by an erosional trend which will remove major amounts of material from storage in the channel, islands and floodplain.;A river chronology is developed which relates physical change in the study area to channel processes reflecting regional land use changes. The most important change has been storage of anthracite coal waste in the channel, islands and floodplain and transformation of material stored in the river bed from natural material to predominantly anthracite coal waste. The diffusion and adoption of Welsh anthracite iron technology in the Susquehanna River Basin in 1840, followed by the development of breaker technology, led to industrialization of the basin and the generation of massive amounts of anthracite coal waste.