Connecticut

Evaluating Hurricane Response in the Connecticut River Floodplain Environment

What: The 2013 project will investigate the impact of Tropical Storm Irene on sediment transport in the Deerfield River Basin. This record-breaking storm dumped 180-250 mm of rain within a 24-hour period causing extensive flooding throughout the watershed. Numerous mass wasting events helped contribute to an anomalously high sediment load.

When: July 1-26

Where: The Deerfield River runs from Greenfield, Massachusetts where it enters the Connecticut River to its headwaters near Wilmington, Vermont. There are a number of dam impounded lakes along the rivers course where we will take sediment cores and collect geophysical data. Students will be housed at Amherst College and we will make day trips to the field. In addition, students will have access to laboratory facilities at Amherst and Smith Colleges as well as at the University of Massachusetts.

Who: Nine students. Professors Anna Martini (Amherst), Jon Woodruff (University of Massachusetts, Amherst), Bob Newton (Smith) and graduate student Brian Yellen (University of Massachusetts, Amherst).

Project Overview and Goals

Understanding how sediment is transported, trapped, and remobilized in low-lying rivers and respective estuaries is of broad geomorphic significance, fundamental to quantifying river inputs to the ocean, constraining internal inventories, and predicting the evolution of low gradient landscapes. Sediment transport processes are, in part, climate controlled and the predicted increase in extreme rainfall events will likely change the dynamics of sediment production, transport, and deposition. Tropical Storm Irene was an example of one of these extreme rainfall events and a study of how and where sediment was eroded and deposited will help us understand how future changes in climate will affect fluvial systems in this region.

In this project we will seek to answer a number of fundamental questions:

• Where did the Tropical Irene sediment load come from?
• What part of the hydrologic system produced the most sediment, higher order tributaries or headwater catchments?
• How important were mass wasting events as opposed to bank and channel erosion in supplying sediment to the river?
• How influential are flood-control projects and land-use changes on sediment yield?
• How does the Tropical Storm Irene deposits compare to earlier historical flood deposits as well as material from more routine seasonal high discharge events?

To answer these questions we will employ the following field and laboratory techniques:

• Mapping of landslides and channel erosion features along selected sections of the Deerfield River and its tributaries.
• Collection of sediment cores from reservoirs and lakes within the watershed.
• Bathymetric surveys and sub-bottom profiling at the core sampling sites.
• Sedimentologic, mineralogic and chemical analysis of all sediment samples.

The study will be organized such that similar methods will be used to examine 3 different size subcatchments within the Deerfield basin from its headwaters to the outlet at the Connecticut River. Students will work in teams, with each team assigned to a particular watershed system.

 

Potential Student Projects

1. Evaluating the Potential Irene Deposit “Marker Bed”. From a series of tributaries we plan to core into natural, beaver and human accumulation pockets to assess the type (source) of these deposits and the rate of pre and post-Irene deposition. The question is whether the event, by excavating huge up-river deposits of glacial materials, has changed the overall sediment supply dynamic of the river system.
2. Characterize the organic matter released during spring freshets, Tropical Storm Irene and “normal” background Organic Material (OM). From the well-distinguished event horizons in a series of sediment cores we will characterize the OM by examining 1) C/N ratios; 2) d13C and d15N values and 3) lipid biomarker concentrations. Specifically we wish to quantify mixing end members between terrestrial and aquatic organic sources as well as waste treatment inputs to the Conn. River system.
3. Detailed GIS mapping of watersheds integrating land-use changes and sediments supply from the various tributaries of the Deerfield. We will integrate our dataset geographically to better assess the historical and future effects of development on the sediment and chemical supply to the river.
4. Historical research into Hg sources, detailed statistical analysis of Hg profiles. We need to decipher the sources of Hg contamination, specifically detangle the atmospheric record in the northeast from the numerous point sources. We will do this by evaluation multiple bog and lake records from the region, gaining an idealized atmospheric profile, subtracting those values and attempting to calculate, based on watershed area and organic matter content, the local Hg load to the river.
5. Evaluating Flood Control Dams – What is the net sedimentological effect of flood control dams in the upper watershed? Can we delineate Irene flooding and previous events in the sediment record? What type of material is preferentially winnowed from the downstream sediment supply versus that which makes it past flood control projects?
6. Characterize the efficiency of lakes and reservoirs to trap sediment released during Tropical Storm Irene (TSI). The gage station for Avery Brook study is located just upstream from the Northampton Reservoir. The total sediment load to the reservoir from Avery Brook will be compared to sediment accumulated in the reservoir. Sediment cores will be taken from the reservoir and analyzed to determine the amount and nature of TSI sediments. Estimates of the amount of TSI sediment in the reservoir will be compared to the amount delivered to the reservoir from Avery Brook.
7. Determine characteristics of the Tropical Storm Irene sediment deposited by the Mill River in Northampton. Paradise Pond is a small Mill River impoundment located on the campus of Smith College. The 135 km2 watershed produces sediment at a rate that requires dredging every 6 to 10 years with the last dredging occurring in 2008. Tropical Storm Irene caused the premature filling of the pond. Sediment cores and comparative bathymetry can be used to determine the nature and extent of sediment released from TSI.
8. Determine the source of Tropical Storm Irene sediment from bank erosion and mass wasting from selected watersheds. There are excellent exposures of Pleistocene sediments from numerous bank scours and landslides formed during TSI in the Deerfield River watershed. This project would use air photos and field reconnaissance together with GIS techniques to document the nature and potential amounts of TSI sediment from these sources.

Recommended Courses

Sedimentology, Geomorphology, mineralogy, Geographic Information Systems.

Working Conditions

Fieldwork will include walking along streams in heavily wooded areas and lake coring from small boats. All students are required to be proficient swimmers. Insect repellent is required as some ticks in the area carry Lyme Disease.

References

• Alto, R., Lauer, J.W., and Dietrich, W.E., 2008, Spatial and temporal dynamics of sediment accumulation and exchange along Strickland River floodplains (Papua New Guinea) over decadal-to-centennial timescales: Journal of Geophysical Research, v. 113, p.
• Patton, P.C., and Horne, G.S., 1992, Response of the Connecticut River estuary to late Holocene sea level rise: Geomorphology, v. 5, p. 391-417.
• Woodruff, J.D., Sriver, R.L., and Lund, D.C., 2012, Tropical cyclone activity and western North Atlantic stratification over the last millennium; a comparative review with viable connections: JQS.Journal of Quaternary Science, v. 27, p. 337-343.