NSF REU Projects - Summer 2015!

Project #1: Quantifying the Role of Vegetation on the Erodibility of Streambanks and Incorporation into Fundamental Cohesive Soil Transport Models (Dr. Fox):

Current streambank erosion and failure models include procedures and equations for the impact of vegetation on increasing the geotechnical strength of the bank sediment. However, only empirical work has been performed to date relating root characteristics to reduced soil erodibility by fluvial forces. Undergraduate students will utilize a jet erosion test (JET) to measure the erodibility characteristics (erodibility coefficient and critical shear stress) of Cow Creek banks stabilized with three different vegetation types and across various growth stages by comparing results over the three years. Students will also collect soil samples for quantifying soil texture, bulk density, and moisture content and vegetation samples for quantifying root characteristics at the time of the JET. Students will quantify root cohesion using root tensile strength tests in the laboratory and root characteristics using the WinRhizo software (root density, average root diameter, and distribution of roots relative to size). These experiments will identify and develop key relationships between erodibility parameters, soil parameters (texture, bulk density, and moisture content) and root characteristics as a function of vegetation type. This research directly supports the long-term research program on streambank erosion/failure of Dr. Fox. The students’ work will lead to the eventual incorporation of resistive forces due to roots into a fundamental detachment erosion model, potentially as a year 3 student project, which could transform erosion and stability modeling.


Project #2: Influence of In-Stream Rehabilitation Structures on Transient Surface and Hyporheic Storage (Dr. Halihan): 

The hyporheic zone is the region beneath and to the sides of the streambed affected by small-scale water exchange between surface stream flow and shallow groundwater. Hyporheic zones support intense biological and biogeochemical activity such as nutrient transformations [30]. Stream bed topographic features (e.g., side pools) and hyporheic zones are often regions where water velocity is slower than that of the main advective flow. The attendant increase in mean residence time due to above- and below-streambed surface storage zones is referred to as hydraulic retention or total storage. Most hyporheic and transient storage research has focused on gravel bed streams with limited work in fine bed streams. The hypothesis in this undergraduate research is that rehabilitation structures such as cross vanes and rock riffle structures promote not only additional surface transient storage but also hyporheic storage even in fine bed streams. Undergraduates will quantify hydraulic retention in reaches of Cow Creek and at stream restoration sites in the Illinois River with and without in-stream structures by conducting conservative tracer and Rhodamine WT transport studies and inversely estimating storage parameters using solute transport models. Drive point piezometers will be used to sample shallow groundwater around the stream structures. Also, electrical resistivity imaging will be used to image solute transport in the shallow groundwater for reaches with and without structures, directly the supporting the research program of Dr. Halihan. Experiments performed each year will be at variable stages (discharges) and therefore will cumulatively quantify hyporheic and total transient storage as a function of discharge. This research could transform the design of structures to promote hyporheic flows.


Project #3: Evaluation of Sediment Effects on Stream Fishes (Dr. Brewer):

Suspended and deposited sediments are pervasive problems for fishes in warmwater streams.  In fact, excess sedimentation from erosion occurs in nearly 50% of all streams in the United States. While streams carry sediment loads as part of natural processes, excess sedimentation causes adverse impacts to aquatic ecosystems.  Increased sedimentation relates to various land-use and riparian practices and increasingly rehabilitation practices are considered to reduce sediment inputs to streams.  The hypothesis of this undergraduate research project is that rehabilitation techniques (e.g., planting riparian vegetation) and structures (e.g., cross veins) decrease levels of suspended and deposited sediment during and after storm events. Undergraduates will quantify levels of sediment in reaches of Cow Creek where rehabilitation practices have been implemented and in reaches with no mitigation. In addition, undergraduates will quantify fish-community structure in adjacent locations to determine if there are implications for the persistence of communities in these areas.  In one of the years an undergraduate project will address the tolerance (growth and survival) of several fishes to varying levels of sedimentation in the laboratory. A recirculation tank will be used to examine fish growth and survival under known concentrations of suspended sediment.  These projects will provide valuable information on the fitness responses of fishes to sedimentation and the effectiveness of rehabilitation techniques, supporting the larger research theme of Dr. Brewer’s laboratory which examines the effects of landscape change on aquatic biota. 


Project #4: Use of Aquatic Macroinvertebrates to Assess Streambank Modifications (Dr. Dzialowski):

Aquatic macroinvertebrates are often used to assess watershed health [41].  Because different taxa vary in their tolerance to disturbances, the presence or absence of specific taxa can be used to assess the condition of a stream either on a particular sampling date or as a stream responds to changes over time.  Understanding how humans impact aquatic ecosystems is the major focus of Dr. Dzialowski’s research and the streambank modifications (e.g., vegetative plantings, alterations of channel slopes) at the Cow Creek site provide a unique opportunity to understand how macroinvertebrate communities respond to improvements in stream and riparian habitat.  The hypothesis in this undergraduate research is that streambank improvements will lead to increases in overall habitat and water quality in stream reaches that have been modified at Cow Creek, which will in turn lead to increases in macroinvertebrate taxa that are less tolerant to disturbance. Macroinvertebrates as well as habitat and water quality data will be collected from areas where streambanks have been modified and compared to upstream and downstream reaches where no modifications have occurred.  In addition, the student will compare macroinvertebrate data from these sites with a large database of macroinvertebrate data from 394 Oklahoma stream sites of varying quality with the goal of developing a broader framework for assessing how macroinvertebrate communities respond to streambank modifications.  Also, by collecting data over three summers the students will be able to determine not only how macroinvertebrate communities respond to streambank modification, but if these responses vary over time.


Project #5: Evaluation of Plant Diversity Response to Streambank Modification (Dr. Fishbein):

The biomechanical and ecological effects of revegetation on restoration of stream function have received considerable study, including in the Great Plains region.  In comparison, the converse effects of stream rehabilitation on restoration of plant communities have been less well studied.  Revegetation strategies for streambanks at Cow Creek have included seeding in cover crops of non-native grain crops (wheat, rye), non-native wildflower mixes, and native species.  These treatments provide an excellent design for studying the recovery of natural vegetation under varying management techniques.  Preliminary data on floristic composition have been collected by students in Dr. Fishbein’s Field Botany course. An REU student each year will participate in vegetation monitoring, using the techniques of floristic inventory, plant identification, plot-based vegetation sampling, and statistical analysis of treatment effects.  In each year and at the end of the project, short-term changes in vegetation composition as well as trends in natural vegetation recovery will be assessed.


Project #6: Assessment of the Short-term Adjustment and Stabilization of Stream Restoration Utilizing Natural Channel Design Concepts (Dr. Vogel): 

One primary motivation of the stream restoration project at Cow Creek was the increasingly rapid erosion on the outer meander of the reach, which was causing the stream to come uncomfortably close to existing infrastructure including utility poles and a shed.  This is a common motivation for stream restoration projects because of the quantifiable economic impact of land and infrastructure loss. In this research project, the students will assess the objective of stability of the streambanks in the short-term (first five years) after completion.  The students will complete similar activities during each of the three years of the REU project to assess changes from year to year and since and before construction of the restoration project.  Activities that the students will complete will include longitudinal profiles and cross sections in Cow Creek and selected Illinois River Sites; installation and monitoring of stream-bottom and bank pins at Cow Creek and selected Illinois River sites; collection of weather data from nearby Mesonet sites; classification of the weather data relative to historic data record; assessment of the channel form utilizing Rosgen’s stream classification method;; characterization local reference stream reach(es) to compare against for the Cow Creek site; assessment of the success of the restoration for the objective of stability; and, identification of alternatives and/or future activities that can improve the restoration to improve stability.

Project #7: Vegetation Induced Changes in Microclimate and Thermal Environment in Riparian Zones and Streams (Dr. Zou):

Riparian vegetation plays an important role in modifying below canopy microclimate, providing suitable habitats for fish and wildlife. Vegetation regulates light and thermal conditions below canopy and adjacent stream primarily through modification of energy input. Altered light condition interacts with water depth and instream sediment condition to affect the photosynthetically active radiation reaching the riverbed (benthic PAR), and therefore the biotic community in the stream. In this research, undergraduate students will utilize a Hemiview Canopy System (Delta-T Devices, England) to qualify a suite of vegetation metrics including LAI and DSF (direct site factor) associated with three different types of vegetation associated with streambanks at the Cow Creek site  (year 1 student); study the temporal dynamics of soil and water temperature using i-Button temperature loggers (Maxim Integrated Products, Inc., CA) for different vegetation types (year 2 student); and investigate the relationship between the vegetation metrics, benthic PAR, and stream water thermal condition using modeling approaches (year 3 student). Results from this project, especially when combined with others in this proposal, will provide information for future restoration design for fish and wildlife habitat.