Sediment Dynamics of the Oneida Creek Delta, Oneida Lake, New York
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SEDIMENT DYNAMICS OF THE ONEIDA CREEK DELTA, ONEIDA LAKE, NEW YORK Eugene W. Domack, Dept. of Geology, Hamilton College, Clinton New York 13323 [email protected] Scott Ingmire, Madison County Planning Office, Katie Arnold, Dept. of Geology, Hamilton College, Clinton New York 13323 9/22/04 (draft) 1 Cover Illustration: Air photo of the Eastern End of Oneida Lake taken in 1985 with features discussed in report and outline of study area. ACKNOWLEDGEMENTS This project was supported through a grant from the Central New York Regional Planning and Development Board and the New York State Department of Environment and Conservation to Hamilton College. A matching award from Hamilton College also provided equipment support for the project. We would like to thank Cap'n Lee Webster for his enthusiastic and professional support of our work on Oneida Lake, Andrew Friedman, and Mitch Ward for help with lake surveys. The advice and guidance of Anne Saltman, Stephanie Harrington, and JoAnne Falukner were appreciated. We also wish to thank Mr. Edward Beickert. 2 EXECUTIVE SUMMARY A study of the sediment dynamics and morphology of the Oneida Creek delta, Oneida Lake New York provides the following conclusions: • The delta at the mouth of Oneida Creek is a wave dominated sand system that extends 1800 ft into Oneida Lake and is incised by a deep channel of Oneida Creek. • The Oneida Creek delta covers an area of lake floor of from 3.53 x 105 to 3.65 x 105 ft2 (~3.20 x 105 m2). It contains an estimate of 1.42 x 107 to 1.73 x 107 ft3 (~3.96 x 105 m3) of sediment and pore fluid, comprising an estimate of 7.72 x 108 kg of solids (sand). • Observed suspended loads and discharge characteristics of Oneida Creek are insufficient to have provided all of the sand within the delta within a reasonable length of time. • Significant sediment sources for the delta must include material resuspended from the eastern shore of the lake, particularly that area from the Fish Creek jetty at Verona Beach to and along Verona Beach State Park. • Exacerbated erosion of the shoreface region of the eastern end of Oneida Lake must be attributed to artificial lowering of the lake level, which extends the normal wave base, in conjunction with diminishment of sand supply from Fish Creek. • Dredging of the Oneida Creek delta to remediate the sedimentation problem will only temporarily alleviate the situation as the system will likely readjust to the new accommodation space provided by dredging. • Suspended loads from Oneida Creek are contributing excess mud (silt and clay) to Oneida Lake but are not considered the major source of sand that currently is deposited across the delta. PROJECT OBJECTIVES One of the main issues of concern outlined in the draft Oneida Lake and Watershed Management Plan is sedimentation from tributary streams. Initial tributary monitoring data from the Oneida Lake Watershed identifies Oneida Creek as the third largest contributor of Total Suspended Solids (TSS) with an average 4,365 g/ha/day during storm events (Figure 1). Using data from a USGS flow monitoring station, daily estimates of TSS ranged from 18,295 kg/day up to 75,282 kg/day. Historic bathymetric maps of the area show that the general depth around the shoreline and creek mouth was about 3-4 feet. A recent bathymetric survey of the area shows that today, much of the area is 3 feet deep or less, with some areas only 1.5 feet deep. This growing deposystem (classified as a wave dominated delta) has caused navigation and aesthetic problems and numerous potential effects on aquatic life in and around the mouth of Oneida Creek. 3 Figure 1: Drainage basin map of Oneida Creek and its tributaries. Although it is believed that anthropogenic influences have greatly increased the rates of natural erosion in Oneida Creek and subsequent deposition in South Bay, this has never been quantified or examined in detail. In addition, the effects of winter draw- down in lake level and subsequent expansion of wave induced sediment transport have 4 never been examined in this area. Both of these factors may play an important role in the sediment dynamics of South Bay and, indeed the entire shoreline of Oneida Lake. Our primary objective for this project was to determine the source of the sediment clogging the area around the mouth of Oneida Creek (OC) and the greater South Bay area. By mapping the wave dominated delta we were able to show in great detail the current morphology of this area and the volume (mass) of sediment contained within the delta. Our sampling and particle size analysis of suspended sediment loads in OC and bottom sediments across the delta have also allowed us to understand sediment delivery to and redistribution with the delta system. Further, sediment cores have allowed us to examine the temporal changes in sediment process over the last 50 years. BACKGROUND Today the Oneida Lake Basin is a highly perturbed system that is not in equilibrium with the natural processes which contributed to its development over the last 11,000 years. Sediment build up along the eastern shore is apparent from the natural history of shoreline progradation, since the basin became an isolated extension of Glacial Lake Iroquois some 11,000 years ago (cover figure). Approximately 1 mile of shoreline advance has taken place in the last 11,000 years with evidence that the rates have not been constant over time (Fadem, 2001; Hickock, 2000). The shorelines are marked by a prominent set of beach ridges and spits that run sub-parallel to the modern shoreline (cover figure). Such periods of episodic shoreline accretion may correspond to natural cycles in lake level fluctuation (climatically driven, Kirby, et al., 2001) or excessive sediment supply from rivers (decadal increases in storminess, also climatically driven). Sediment progradation (build out) is a natural process of the lake basin, especially along the eastern shoreline. However, the pattern and localization of sediment accretion at the mouth of Oneida Creek in tandem with erosion along the shoreline to the north is not an obvious natural pattern. Hence, the eastern shoreline is a good example of how human activity can disrupt a coastal system. The factors contributing and effecting sediment distribution along the eastern shoreline include: • wave processes • fluvial (river) processes • lake ice processes Of the above, wave processes are the most important as Oneida Lake has a long fetch due to its orientation parallel to the prevailing westerly winds and shallow depth. The waves influence the direction of nearshore drift and transport of shoreline sediment parallel to the shore and the resuspension and sorting of bottom sediment during periods of extended wave base, as during storms and during periods of lake level drawdown. Since 1952 periods of lake level drawdown have extended the wave base to greater areas of the bottom than under natural conditions. This leads to resuspension of the fine fraction (fine-grained sand and mud) especially after periods of ice cover that retard wave activity and allow settling of fines during the winter. Fish Creek and Oneida Creek represent the major river inputs at the eastern end of the lake (cover figure). Fish Creek is the much larger and more dynamic of the two systems and is primarily a bedload (sand) dominated system while Oneida Creek is a 5 suspended load (mud) dominated system. Since the excavation of the NY State Barge Canal delivery of the bedload (sand) to the eastern shoreline of the lake has been interrupted and today base level for Fish Creek begins at its juncture with the canal. This results in excessive sedimentation at the confluence which is remediated by the bi- annual dredging of sand from this site. As a result the normal load of sand to the wave dominated system on the eastern shore of Oneida Lake is no longer in place and the shoreline communities of Sylvan Beach and the Verona Beach State Park have had to resort to beach nourishment in the past decade to counter shoreline erosion. Erosion of the shoreline is exacerbated by continued subsidence (compaction) of the coastal plain that is not balanced by natural sediment delivery by Fish Creek. Oneida Creek is also a perturbed system as its drainage basin (Figure 1) has undergone rapid development over the last half century. Such changes in land use, paved versus vegetated or agricultural landscape influence runoff and sediment yields. Such land use changes combined with the high degree of susceptibility of the soils/bedrock within the drainage result in a system that contributes to the sediment loading problems within Oneida Lake. The toxicity of the sediment supplied by Oneida Creek is also a concern because of the industrial and intense agricultural nature of some of the drainage area. The questions we attempt to place into perspective in this report deal with the relative influence of river, storm, and coastal (wave dominated) processes on the submerged delta off of Oneida Creek. It is apparent from our investigations that the excessive build up of sediment at the mouth of Oneida Creek is the result of a combination of the processes discussed above. Restoring open access to the mouth of Oneida Creek and preventing further sediment accretion at the site is a goal to be considered. However, such a solution to the problem will be realistic only if all the components to the equation are considered, including: • altered wave base due to lake level lowering • beach nourishment and erosion at Verona Beach State Park and longshore transport of sediment toward and across the delta • sediment supply from Oneida Creek • subsidence of coastal plain in vicinity of the mouth of Oneida Creek To address these issues we conducted several lines of research and observation that are outlined and discussed in the text of this report.