“Inter- pref. 1. Between or among 2. Mutually: together” <interdisciplinary <interagency <intertwine <interactive
“Inter” is the overarching element for the Island 63 study. These key words describe an innovative project through which an interdisciplinary team of river engineers, biologists, scientists, and other experts are working as one team across organizational and professional lines to determine how a pristine habitat is closely intertwined with the river’s various flows. Technologies developed at Island 63 will be applied up and down the lower Mississippi River to enhance management strategies and to improve knowledge of the river’s impacts and importance to the environment.
The wild and scenic Island 63 is located at river mile 639, roughly 12 miles northwest of Clarksdale, Mississippi. The study area includes thousands of acres of floodplain area between the main river channel and the river levee along a 35- to 40-mile reach of the river. Island 63’s secondary channels, chutes, scour holes, lakes, and borrow pits are greatly dependent on and impacted by variations of the Mississippi River. Floods can inundate the entire area; low river stages leave the woodlands dry except for the area’s numerous water bodies.
But while Island 63 is a productive habitat for many diverse animal and fisheries communities, human activities and river operations have greatly influenced water flow, sediment transport, and habitat complexity. That all comes together to make this the perfect pilot for this two-year initial, interdisciplinary effort, to see how it can all continue to thrive together.
Geomorphology
Charlie Little, a research hydraulic engineer at the Army Corps’ Engineer Research and Development Center, is the co-lead for the Island 63 geomorphic assessment portion.
“We are studying the hydraulic connections of the Mississippi River to all the water bodies in and around Island 63 at all river stages. This includes monitoring and determining the characteristics that impact the fisheries,” said Little.
The assessment includes installing temporary gauges at various locations to monitor connectivity between the river and the other water bodies and see how water moves through the entire system, including its frequency, timing and volume. And it is critical to all river efforts.
“The new Mississippi River Geomorphology and Potamology Program is focused on the entire lower river,” Little said. “What are the changes in channel geometry, sediment loads and budget, and other factors? We use these data to determine what the river has gone through, how it is today, and what to expect in the future.”
As part of the Island 63 geomorphology assessment, the team has historic river data and readings dating back to 1915, including 1940s data, and information representing every decade from 1960 on. That data reveals river trends, such as major impacts from the 1930s and 1940s due to cutoffs, Little said. From Memphis, Tennessee, to Vicksburg, Mississippi, the original river channel was approximately 500 miles long. The cutoffs shortened the meandering river channel by roughly 150 miles.
“The cutoffs caused river to downcut or incise its channel. The shortened river responds to the increased slope by incising the main channel.”
Ecohydrology
The ecological, or ecohydrology, assessment is integrating physical and biological processes, focusing on diversity among the habitats, how the hydrologic connectivity influences habitat diversity, and the impacts on spawning and rearing of fishes.
Dr. Jack Killgore, a research fisheries biologist at the Engineer Research and Development Center and team leader for the ecohydrology effort, is managing a wide range of sampling activities and habitat analyses.
“No one ever put together a joint effort like this,” said Killgore. “The Mississippi River Geomorphology and Potamology Program is making this happen. This is a whole new opportunity for a comprehensive, holistic effort.”
The team is using trotlines, trawls, gill nets, and seines to sample adult and juvenile fish and light traps to collect larval fish and aquatic invertebrates. Adult fish are measured, marked with external tags and released. Juvenile and larval fishes and benthic macroinvertebrates are preserved and transported back to the laboratory for analysis. A statistics package is used to collect and analyze all these data.
“We are developing guidance that will be useful on the entire lower Mississippi,” said Killgore. “There are more than 10 river cutoffs that still have connections to the river that are unimpeded by levees. These important cutoff areas still function as a natural part of the river.
“We’ve made headway with the river engineers; we are learning from them. River engineers deal with the river’s long-term impacts, over decades. As biologists, we deal with short-term impacts, or year to year variations. We have a whole generation of new biologists that are growing up with new river engineers. The future looks great for Mississippi River projects from an interdisciplinary standpoint.”
Numerical Modeling
The final, numerical modeling stage, is at a very early stage, said Dr. Andy Gaines, a research civil engineer and regional technical specialist with the U.S. Army Corps of Engineers’ Memphis District, but the team is looking at late 2015 as a completion date for a modeling effort that will connect the river hydrodynamics, sediment and environmental habitat.
According to Gaines, the modeling efforts have two major elements. One is a research element focused on the interaction of the river and floodplain with the environment. The other is supporting current and future operations to restore water flow in secondary river chutes and channels. Over the last decade or so, Killgore’s fish teams have identified the importance of secondary channels as habitat and investigated ways to improve these areas. One method is to notch river dikes, allowing river flow into secondary channel areas.
“The modeling focus is on the development of tools—in the case models—to apply at other locations for similar benefits as Island 63. In 2006, for example, a dike was notched at Island 63. How did the notch improve habitat conditions? How can the success at Island 63 be applied elsewhere on the river?
“There has never been such a joint study on the lower Mississippi, so this is the pilot study. Our focus is integrated science that can be applied elsewhere. Bringing all these interconnected things together, not just navigation or flood risk reduction, but the environmental aspect, is very important. How can we tweak navigation or flood projects for wildlife improvement? It is critical for the future of the river.”