How Does It Work?
One method that is sometimes used to help address nitrogen/nutrient pollution in bays and estuaries is widening and deepening of the associated inlets in order to increase ‘flushing efficiency’ by increasing the volume of water flowing into and out of them. The objective is to allow more clean ocean water into the bays and estuaries and more nutrient-rich, polluted water out into the open ocean, thereby improving water quality.
What Are the Advantages?
Inlet Widening is often a considerably more cost-effective way of reducing nitrogen loads than sewering.
What Are the Potential Disadvantages?
There are a number of potential drawbacks to inlet widening, which must be fully explored before a decision is taken to use this approach, including:
- additional flooding to property due to enhanced tidal flow and water levels;
- additional erosion inside the inlet due to greater current action;
- the need for new construction or modification of rock jetties for inlet stabilization;
- the need for additional maintenance and routine dredging of the inlets;
- the need for modifications to existing state and federal permits for dredging;
- the need for new construction or modification of bridges and roads at the inlets;
- impacts on biologic conditions in the estuary; and,
- the flushing of significant quantities of organic debris and nitrogen-rich water through the inlets to the adjacent coast and nearshore waters*
*Thus far, dilution in nearshore waters has not been shown to adversely impact water quality. Nearshore areas off of Great and Green Ponds, for example, which have efficient tidal inlets that flush estuarine nutrients offshore, are reported to have similar water quality to Bournes and Little Ponds,which have restricted inlets that are not effective in flushing nutrients offshore).
Inlet Widening in Falmouth
The Town of Falmouth has been exploring the possibility of widening inlets as an alternative to sewering in certain areas for some time now. In 2006, the Massachusetts Estuaries Project (MEP) performed an evaluation of Falmouth’s bays and estuaries and determined that in certain areas, such as LIttle Pond and Bournes Pond, inlet widening could be a cost-effective strategy for reducing nitrogen loads. Since then a series of discussions, appropriations and evaluation projects have taken place, resulting in a detailed plan for widening Bournes Pond Inlet. For details on the history of the project, its specifics, and its current status, please visit the Town of Falmouth Inlet Widening Page.
Falmouth Water Stewards has been intimately involved in these discussions from the beginning. Two of our board members sat on the original Water Quality Management Committee and we have worked closely with members of the current Water Quality Management Committee since its inception. FWS board member, S. Jeffress Williams, a well-known coastal geologist, wrote an article on the proposed widening in our Newsletter in 2014. Jeff has been a key contributor to discussions about the widening of Bournes Pond Inlet, and was asked to review and comment on the Bournes Pond Coastal Erosion and Flooding Analysis Report. His comments are integrated into the final report here.