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Land and Stream Sediment Process Restoration in An Agricultural Watershed


Objective 1. Fluvial Sediment Processes. Characterize current stream channel geomorphic conditions, describe the change in stream morphology over time and the degree of departure from reference-reach conditions, and relate current and reference conditions to hydrologic (discharge and timing) and sediment transport variation. Hypothesis: The stream channel exhibits a high degree of departure from historic and reference conditions, and this departure contributes to the current degraded water quality condition. <P>Objective 2. Watershed Sediment Budget. Quantify the sediment and discharge budget using overland, ephemeral gully, and stream (bed and bank) processes within a highly agricultural Great Plains watershed. Hypothesis: Current and recent historic watershed conditions have substantial sediment pollution contributions from both overland and fluvial sources. <P>Objective 3. Restoration Scenarios. Use calibrated watershed and stream models to describe current conditions. Develop scenarios for attaining stable land and stream function. Hypothesis: Stakeholder water quality goals cannot be reached without altering both overland and fluvial contributions to sediment loads.<P> Objective 4. Extension Programs. Develop and deliver educational programs, targeted at the most significant contributing areas and sources, that will 1) educate and motivate agricultural producers and other citizens to implement practices that will reduce sediment contamination in the study watershed; and 2) provide information to decision makers and farmers allowing them to make informed decisions for prioritizing where land management changes within the watershed will have the greatest impact in reducing sediment loading to streams. <P>Objective 5. Watershed and Fluvial System Education. Improve education of watershed and fluvial systems at Kansas State University, including development of a new university certificate program, appropriate new course(s), and course modules and experiential-learning activities within existing courses that allow students to study and integrate knowledge of watershed and fluvial processes.

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Non-Technical Summary: Sediment (soil) is a leading cause of stream and lake impairment in the U.S. Tuttle Creek Lake (a man-made water-supply, recreation, and flood-control reservoir near Manhattan, KS and the target watershed for this study) has become almost half full of sediments and is projected to fill its sediment storage volume by 2023. Soil is everywhere, however, so it's no easy task to find where and when the soil filling the lake is coming from or to develop a plan to solve the problem. This project will use field research to learn more about the current and historical sediment sources in this watershed, computer modeling to predict how future practices will change sediment delivery to the lake, outreach to help stakeholders use this new knowledge to make land-management decisions that reduce sediment sources, and education of college students about land and stream sediment sources processes to help train future leaders and technical source-people. The new knowledge gained in this project about sediments sources and delivery processes, modeling techniques, and methods of disseminating this information to the public will have direct impact on Tuttle Creek Lake and will help researchers and stakeholders in other watersheds in Kansas and the U.S. address similar stream and lake sediment problems. <P> Approach: Objective 1: Fluvial Sediment Processes. We will assess current and historical stream bed and bank sources. (A) Suspended sediment transport will be monitored during and after significant storm events in 4-5 watersheds using both continuous (in situ turbidity) and discrete (TSS sample analysis) techniques. (B) The sediment loads mobilized over time from streambanks will be calculated using both long-term historic analysis, using aerial photographic analysis, and short-term geomorphic monitoring. Comparison of undifferentiated sediment with soils horizon development can be used to identify and measure over-bank sedimentation. Current streambank erosion rates will be monitored using a proven method (Rosgen, 1994). In each of 4-5 reaches, we will survey and map channel profile, dimension and pattern on an annual basis during the three years of this study; monitor streambank erosion rates using bank (erosion) pins and precise bank profiles; install and monitor scour chains in the channel bed to will provide data on scour depths for given flow events and features of the channel bed. (C) Stream channel stability and function will be evaluated using several methods, including BEHI, NBS, Pfankuch and SVAP assessments; bed and bank form change measurements at monumented cross sections; and surveys of riparian vegetation communities. Objective 2: Watershed Sediment Budget. The sediment from both typical sheet and rill erosion and under-documented ephemeral gully erosion will be evaluated for upland sources (primarily agricultural fields). The AnnAGNPS model will be used to estimate sheet and rill contributions resulting from upland sources. The Revised Ephemeral Gully Erosion Model (REGEM) has recently been incorporated into the AnnAGNPS model, and will be used to estimate sediments losses from upland gully sources. Objective 3: Restoration Scenarios. Various management practices for controlling sediment transport will be evaluated by integrating stream survey, GIS and model information. The CONCEPTS model (simulates unsteady, one-dimensional open-channel hydraulics, graded-sediment transport, and bank-erosion processes in stream corridors) will be calibrated to simulate streambank failure events using data collected from one of the stream reaches between upstream-downstream monitoring stations. An integrated AGNPS-CONCEPTS model will evaluate effects of changing sediment delivery from the landscape on stream channel evolution and stream bed and bank erosion. Objective 4: Extension Programs. The project will develop the tools and models to educate the decision makers in the watershed enabling them to make informed decisions; host an annual meeting with all stakeholders to present results; and develop two popular publications to be used in meetings with local citizens and with decision makers. Objective 5: Watershed and Fluvial System Education. Our goal is to position Kansas State Univ. as the leader in fluvial systems and watershed science and restoration in the Great Plains Ecoregion. Toward this goal, a need exists for more concentrated, interdisciplinary study of fluvial systems and watershed science at Kansas State Univ.

Douglas-Mankin, Kyle
Kansas State University
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