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Final Report: Role of land use and BMPs in reducing the effect of extreme magnitude events on sediment and pollutant transport in the SE US Coastal Plain and Mississippi Alluvial Valley

EPA Grant Number: R835186
Title: Role of land use and BMPs in reducing the effect of extreme magnitude events on sediment and pollutant transport in the SE US Coastal Plain and Mississippi Alluvial Valley
Investigators: Hatten, Jeffery A
Institution: Oregon State University
EPA Project Officer: Packard, Benjamin H
Project Period: April 1, 2012 through March 31, 2017
Project Amount: $363,258
RFA: Extreme Event Impacts on Air Quality and Water Quality with a Changing Global Climate (2011) RFA Text |  Recipients Lists
Research Category: Climate Change , Air Quality and Air Toxics , Watersheds , Air , Water

Objective:

The overall objective of this research is to determine the role of best management practices (BMPs) and land use decisions in affecting water quality in the face of extreme events and climate change.  Two objectives have been developed to guide this research:

Objective #1. Determine the capacity of BMPs to reduce large event caused delivery of sediment in a lake with small agricultural watershed in the Mississippi Alluvial Valley.  Our working hypothesis is that the efficiency of BMPs at reducing sediment and pollutant yield will decrease with increasing storm magnitude. 

 

Objective #2. Determine the role that BMP development and landuse decisions have had on event associated sedimentation rates in a lake with a large watershed.  We hypothesize that in a large watershed (Loon Lake watershed in the Oregon Coast Range) that the response of sedimentation to BMP and/or Oregon Forest Practices Act implementation will be much slower as a result of large stores of sediment deposited as a result of historical landuse in locations proximal to the river. The flux of sediment from these sources is likely to be affected by a change in river discharge as a result of climate change.

 

Summary/Accomplishments (Outputs/Outcomes):

 
Objective #1
We received one core from the USDA-ARS National Sedimentation Lab (Oxford, MS) from Beasley Lake in the Mississippi Delta (9.15 km2). This lake’s sedimentation rates were previously described and found that the installation of BMPs in 1994 led to significant  (76%) reductions in the sedimentation rates. We were unable to identify events or annual layers.  Sediment in this lake were not preserved in layers due to high biotic activity at the sediment water interface.  We were able to discern trends in sediment characteristics over time and our analysis was limited to examining the change in sediment source over time in this managed system.
 
Objective #2
We collected several cores from Loon Lak, an Oregon Coast Range Lake with a history of settlement and timber harvesting.   Loon Lake (230 km2) is about 89% forested with over 70% owned by one major private timber landowner, allowing us a unique view into the impacts of management and BMP changes in a large watershed.  We chose to focus our analytical efforts on cores collected from the deepest part of the lake. This location included multiple cores and we used 7m Nesje core to characterize the long term sedimentation patterns and sediment characteristics in this watershed (514-2013 AD).  Sediment preservation in these cores allowed us to distinguish annual deposition (i.e. varves) back to 1939.  Preservation of varves prior to 1939 was rare, but events (e.g. floods) were evident and preserved throughout the core. We were able to compare pre-settlement (514-1770), post-settlement/pre-regulation (1939-1978), and post-settlement/post-Oregon Forest Practices Act (OFPA; 1978-2013). 

Conclusions:

BMPs and sediment sources and fluxes (Objective 1 & 2)

In general, we find that currently the sediment characteristics in the MS Delta were very different now than they were before land-use was intensified around the end of the Civil War (Objective 1). This is largely due to the drastic change in hydrologic processes due to the disconnection of Beasley Lake from its associated river (The Big Sun Flower). BMPs appear to have drastically reduced sedimentation and this is reflected in a sediment source that appears to be driven by erosion and transport processes that have much lower power than historically.

In the larger watershed We found that state level policies of forest harvesting BMPs were associated with lower annual sedimentation rates (Objective 2). These overall sedimentation rates of the period in which BMPs have been used were not different from the pre-settlement period, with and without large events.  However, we are unable to separate the effects of BMPs from regional climate shifts over the same time period. Current work on contemporary harvesting effects on suspended sediment source and fluxes is being finalized and will dramatically improve the interpretation of our sediment core work.

 

Interaction of extreme events with BMPs to influence sediment sources and fluxes (Objective 2)

We also examined the role of high magnitude events and found that the recurrence interval of events increased after settlement and timber harvest of the watershed (Objective 2-only). While we saw a decrease in overall sedimentation after wide-spread BMP implementation, there appears to have been little effect of improved practices on sedimentation driven by high magnitude storm events. It is possible that timber harvesting (with or without BMPs) is increasing the incidence of high magnitude sedimentation events in the lake, but these events may be interacting with settlement, landuse intensification, and hydrologic alteration that has occurred on the valley leading to the lake.


Journal Articles on this Report : 1 Displayed | Download in RIS Format

Publications Views
Other project views: All 15 publications 1 publications in selected types All 1 journal articles
Publications
Type Citation Project Document Sources
Journal Article Richardson K, Hatten J, Wheatcroft R. 1500 years of lake sedimentation due to fire, earthquakes, floods and land clearance in the Oregon Coast Range:geomorphic sensitivity to floods during timber harvest period. EARTH SURFACE PROCESSES AND LANDFORMS 2018;43(7):1496-1517. R835186 (Final)
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