Landscape History

A review of land use history helps in

1. developing an understanding of the activities that have been occurring and their extent and nature; and
2. characterizing trends over time and associated impacts for various land uses.

For example, in the Piedmont region of the Eastern United States, tobacco farming on steep, erodible slopes caused excessive sediment delivery to stream channels during the 19th and 20th centuries. Since then, the landscape has reverted to deciduous forests, reducing sediment delivery. In many of those locations today, the streams have been downcutting into the erosional debris associated with past land uses and practices that have long since been discontinued.

Channel evolution associated with successional stages of channel adjustment and flow-related sediment increases needs to be assessed for such streams. In the West, many riparian areas along major rivers are recovering due to significant reductions in livestock numbers since the late 1800s. It is important to understand time trends in landscapes and associated changes in river stability and sediment supply, even at this broad level of assessment.

There are few universally available sources of information on landscape history. Comparing aerial photographs from the 1930s or 1940s to more recent photos from the 1970s may provide substantial insights on land use changes over the past several decades, but many sediment-related land use changes preceded the availability of aerial photos. Resources such as Sanborn Fire Insurance Maps  predate aerial photos and may provide detailed insights on industrial activities in urban areas. Consulting historians, local government records, historical property records, and other sources may be necessary if a water body's sediment problems appear to be related to land use history. Using the attached Worksheet 1a: a simple checklist of activities can help in the initial tracking of watershed activities past and present that may influence sediment supply and river stability.

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