Federation Blog

Much of the current thinking about the health of the Chesapeake Bay and its rivers centers on the way that the land around them - their watersheds - are used.  For instance, is the landscape dominated by agriculture and forest or perhaps by roads and suburban development?  Based on these contemporary land uses and a variety of scientific assumptions, models have been created to estimate pollution loads to various waterways, and to drive the restoration strategies for restoring their health.  

So, on the eastern shore of Maryland, where various agricultural land uses such as row crops and the poultry industry pre-dominate, strategies generally focus on maximizing soil conservation practices, like cover crops and forested buffers, and reducing fertilizer loads.  On the western shore, which was once heavily agricultural, but is now primarily urban and suburban development, the problems are attributed largely to “stormwater,” a catch-all term intended to cover anything associated with the runoff of rain from the developed landscape.    Both sets of assumptions seem intuitively true and have a straightforward appeal:  “We do X and Y happens.”   The trouble is, as is so often the case, the world is more complicated than that.

Research coming out of Franklin & Marshall University over the past several years has taken to examining the way that historical land use, primarily agriculture and land clearing, has both shaped our contemporary sense of what healthy streams and creeks look like, but also how they function.  Their research has focused primarily on mill dams throughout the mid-Atlantic, and looking at how sediment released through historical land use built up behind those dams in stream valleys across the region, and is now being exported downstream.   Even where mill dams were not present – and they occurred in significant numbers in Anne Arundel County – the stream valleys are covered in several feet of historical sediment which continues to make its way to tidewater.    

The researchers from Franklin & Marshall issued the following stark statement in the conclusion to a 2011 publication[1]: “incised, post-dam breach streams and fine-grained banks in the mid-Atlantic region are anthropogenic in origin, and the causes of both the accumulation of sediment in valleys and subsequent incision and erosion are not directly related to modern upland land use or cover. Conceptual and computer models that link channel condition and sediment yield exclusively with contemporaneous upland land use, sediment supply and runoff are incomplete because anthropogenic forcing has impacted valley bottom, not only upland, boundary conditions, and has done so for centuries.”

What this means in plain English is that, in many respects, we are still paying for the ways that our predecessors used the land that we currently live on for the past several centuries.  This is not to absolve current generations of taking responsibility for the problem – if not us, who?  If not now, when? – but instead to emphasize that what we do today has long lasting effects and that in order to best restore the health of our waterways, we need to first truly understand what is making them sick.