Though they seem permanent, lowhead dams that straddle creeks and streams throughout the the northeast United States are threatened by a movement to rid watersheds of their industrial features and to restore habitats to their prehuman states. These dams frustrate aquatic biologists, landscape architects, and ecologists who want unobstructed passage of spawning fish deep into watersheds. Within Philadelphia’s Fairmount Park system, several weakened or compromised dams — some dating from the late 17th century — have been removed with financial support from organizations like Trout Unlimited, one of many watershed restoration advocacy groups working to improve Pennsylvania watersheds depleted by industrial pollution.
Just recently, members of the natural lands reclamation division of the Fairmount Park Commission effected the removal of the Holmesburg Dam (1699): a structure of unquestionable historical significance that powered a combination sawmill and gristmill for much of the 18th century. The dam was the last vestige of a complex that one stood on the distant fringes of an international colonial trade network. At high tide, grain and lumber from the mill complex south of Frankford Avenue was shipped via shallow draft boats to Philadelphia and distant colonial ports.
Weakened by floods, the dam was breeched by Park ecologists to allow fish passage. Most other dams in Fairmount Park waterways dating from the 1920s-1930s were designed to create recreational swimming holes. Though structurally sound, these dams lack the historical weight of Holmesburg and are similarly threatened.
The debate over the value of these structures suggests two different visions for America’s urban parks. Although park officials in the early 20th century demolished mill buildings and make-work crews planted trees during Roosevelt’s WPA, prior to the emergence of an ecological worldview stressing biotic interconnectedness these efforts to restore natural lands were motivated by primarily aesthetic considerations. Yet the move to reform these former industrial zones into pristine prehuman habitats conflicts with the initial purpose of parks: to serve humans. As outgrowths of culture, these structures are artifacts and suggestive of an era when society was dislocated for the sake of production. Although dam removal advocates suggest that humans will benefit from improved fishing, other urban park users will suffer from a depleted cultural landscape. Fish passage advocates also point to the existence of a natural history of fish: that the story of navigable rivers preceded that of waterpower and colonial industry.
In the absence of a strong preservation rationale, why protect these dams? Surely the dams might recall the industrial heritage of the valleys but most are not attracted to them for this reason. As landscape architects have long understood, spaces are perceived by a variety of senses and special attention should be given to auditory and olfactory sensations within new spaces. Sound, according to landscape architect Jere Stuart French in City Landscape, fosters attachment to space and “plays upon our subconscious comprehension, which tends to result in our liking or disliking a place but not knowing why.” The sound of water cascading over a lowhead dam, producing white noise, creates a zone of contemplative serenity. While people pay $50 for a non-looping white noise machine, dams cost nothing to produce organic white noise of infinite variety. Visually, cascading water is one of nature’s most captivating forms.
It is worth remembering that preservationists do not speak vacuously when they refer to a “cultural landscape” of which dams are a part. Once utilitarian, these structures reflect humans’ enjoyment of simple pleasures. Now they are locales where humans collect themselves and chart their paths — modern versions of oracular or sacred space. In our effort to write a natural history of fish we must not to forget that a park’s structures are but history writ spatially and that parks began as fundamentally restorative places for humans.