2007 Annual Report 1a.Objectives (from AD-416) Assess the processes of rill and ephemeral gully development, their evolution, and their effects on soil loss, soil degradation, and agricultural resources and productivity across a range of temporal and spatial scales and management practices. Gully erosion represents an important, if not the dominant, sediment source within watersheds in the U.S. and worldwide. 1b.Approach (from AD-416) Develop and execute novel experimental programs to understand the processes leading to the initial growth and development of rills and gullies under varying hydrologic and topographic conditions. Define the key pedologic, hydrologic, and hydrodynamic parameters that control the magnitude, morphology, and rate of soil loss, gully erosion, and landscape degradation due to gully development. Develop theory and equations to predict soil loss and gully erosion on hillslopes and agricultural fields under different management practices and integrate these into USDA watershed and soil erosion models. 3.Progress Report This report serves to document research conducted under a Specific Cooperative Agreement between ARS and the University of Buffalo. Additional details of research can be found in the report for the in-house project 6408-13000-017-00D, "Integrated Assessment and Analysis of Physical Landscape Processes that Impact the Management of Agricultural Watersheds." Work was focused on assessing the longterm effects of tillage practices on ephemeral gully erosion and soil loss, and submitting a collaborative grant application to the National Science Foundation to further study soil erosion. Follow is a brief summary of these recent accomplishments: (1) Ephemeral gullies can serve as a major source and transport mechanism of sediment from upland areas. Yet it is still unclear whether the common practice of tilling agricultural fields to obliterate such gullies on an annual basis affects soil erosion and landscape degradation over the long term (decades). A simple numerical model for ephemeral gully erosion was used to assess soil losses from agricultural fields over a 10-year period. The results indicate that routine filling of ephemeral gully channels during tillage practices greatly increases the likelihood of long-term soil degradation, demonstrating a further advantage of adopting no-till conservation practices. (2) The development and migration of headcuts in rills and gullies can adversely impact soil resources in agricultural areas and accelerate landscape degradation worldwide. Yet the further understanding of these important geomorphic features, and their integration into soil erosion and landscape models, is limited due to the paucity of experimental data. A collaborative research grant between the University at Buffalo and the USDA-ARS was submitted to the National Science Foundation to define experimentally the characteristics of developing and actively migrating headcuts in upland concentrated flows unconstrained by channel width and in response to an upstream sediment supply. This grant application was successful, providing $93,711 in funds starting Fall 2007. Project progress was monitored through frequent conference calls, and documented in three proceeding papers and five journal articles.