Examining the Sedimentary History of Virginia Beach Lakes

Description/Abstract/Artist Statement

While there are no natural lakes in the City of Virginia Beach, there exist dozens of human constructed and/or maintained lakes and reservoirs. In recent years, local residents have experienced water quality impairments including algal blooms and fish kills, which are anecdotally attributed to the problem of “sediment infilling.” In the Summer of 2023, we collected sediment cores from two lakes to address residents’ concerns and examine the recent history of sediment accumulation. These lakes were constructed between 80 and 160 years ago, in areas that previously would have been connected to the Chesapeake Bay.

After bisecting and describing the cores based on visual inspection, we performed a variety of analyses to distinguish distinct lithologies representative of the depositional conditions under which they formed. The specific analyses include loss on ignition to estimate total organic matter, porosity to infer sediment bulk density, and wet-sieving to determine the fraction of sand and mud-sized particles, which reflects the overall depositional energy.

Cores from both lakes reveal finer-grained, organic-rich sediment in the upper ~30 cm, overlying sandy mud with low organic content, which we interpret as pre-lake tidal lagoon sediment. We estimate sedimentation rates ranging from 0.20 cm/y to 0.36 cm/y, suggesting that “sediment infilling” is not likely the culprit causing water quality problems. In one core, we observe multiple buried peat layers, which may reflect a history of marsh inundation or channel migration, which future research can investigate more thoroughly.

Presenting Author Name/s

Kaitlyn Gross

Faculty Advisor/Mentor

Rip P. Hale

Faculty Advisor/Mentor Department

Ocean and Earth Sciences

College Affiliation

College of Sciences

Presentation Type

Poster

Disciplines

Geology | Sedimentology

Session Title

Poster Session

Location

Learning Commons Lobby @ Perry Library

Start Date

3-30-2024 8:30 AM

End Date

3-30-2024 10:00 AM

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Mar 30th, 8:30 AM Mar 30th, 10:00 AM

Examining the Sedimentary History of Virginia Beach Lakes

Learning Commons Lobby @ Perry Library

While there are no natural lakes in the City of Virginia Beach, there exist dozens of human constructed and/or maintained lakes and reservoirs. In recent years, local residents have experienced water quality impairments including algal blooms and fish kills, which are anecdotally attributed to the problem of “sediment infilling.” In the Summer of 2023, we collected sediment cores from two lakes to address residents’ concerns and examine the recent history of sediment accumulation. These lakes were constructed between 80 and 160 years ago, in areas that previously would have been connected to the Chesapeake Bay.

After bisecting and describing the cores based on visual inspection, we performed a variety of analyses to distinguish distinct lithologies representative of the depositional conditions under which they formed. The specific analyses include loss on ignition to estimate total organic matter, porosity to infer sediment bulk density, and wet-sieving to determine the fraction of sand and mud-sized particles, which reflects the overall depositional energy.

Cores from both lakes reveal finer-grained, organic-rich sediment in the upper ~30 cm, overlying sandy mud with low organic content, which we interpret as pre-lake tidal lagoon sediment. We estimate sedimentation rates ranging from 0.20 cm/y to 0.36 cm/y, suggesting that “sediment infilling” is not likely the culprit causing water quality problems. In one core, we observe multiple buried peat layers, which may reflect a history of marsh inundation or channel migration, which future research can investigate more thoroughly.