Kevin Dahms

Kevin Dahms

The results from this study can inform management decisions with regards to small urban estuaries that face immediate challenges associated with ecological degradation and long-term risks related to sea level rise.

2017 Urban Fellow

Research Topic: Water Quality and Hydrology

Faculty Advisor: Gaboury Benoit

Short-term Sediment Dynamics of Urban Estuaries under Altered Tidal Conditions

Estuaries along the Connecticut coast are important ecosystems that provide wildlife habitat and services such as water quality improvement and flood mitigation. However, given the high rate of urbanization in Connecticut, these ecosystems are often degraded by point and non-point source pollution, and the disruption to sediment supply and stormwater flows associated with land use changes. Sea-level rise introduces another threat to these ecosystems. Understanding the physical, biological, and chemical processes of estuaries is essential to their preservation and restoration. Sediment transport represents one of the key processes that drives estuarine ecosystem functions and influences the movement of pollutants in estuaries. Our study informs this field through a novel estuary-scale experiment analyzing the effects of altered tidal flow and water levels on short-term sediment dynamics.

A previous study demonstrated that the Mill and West River estuaries in New Haven, CT have nearly identical watershed sizes, land uses, and share comparable tidal patterns and hydrology. They also contain dynamic tide gates that allow controlled alteration of water level and tidal range in each system. Manipulating the tide gates by going from closed to open Self Regulating Tide Gates in one system, we can create conditions associated with sea-level rise (treatment), while maintaining a control estuary. We use the naturally occurring radionuclide, 7Be, as a sediment tracer. 7Be sorbs to particles quickly and has a short half-life (53.3 days), which makes it ideal for studying estuarine processes. By creating a 7Be mass balance for estuary and combining this data with water budgets, we can produce sediment and contaminant balances over time under different water levels and tidal fluxes.