Long Island Sound river flow

Fig. 15. Boundaries of the lake that occupied the basin of Long Island Sound before the sea reached the elevation of the sadle on the Mattituck sill. The Connecticut River (CR) did not flow into this lake.

The specific dissipation due to river power is most likely to be important near the head end of an estuary, but in some estuaries where the discharge is very large and the tide weak, power from the inflow of fresh water may dominate throughout. The specific dissipation due to the fresh water flow is 7 dSu, where is the mean flow speed, S the slope of the water surface, d the depth, and 7 the unit weight of water. Long Island Sound has no significant area where the specific dissipation due to fresh water inflow is dominant. In the estuary of the Connecticut River it is expected that river power will be a significant fraction of the tidal power when the river is in spate, but detailed calculations have not been done. 

One difficulty with this hypothesis for the denudation of the bedrock surface under the Sound is that there are deep basins north of the mapped edge of the cuesta that could not have been excavated by the proposed river system. These are shown by the shaded areas in Fig. 2. They are thought to be formed on the Fall Zone surface but they may be closed off by outliers of Coastal Plain sediments. Some river valleys on the Fall Zone surface have been overdeepened by subsequent glacial erosion (the Quinnipiac River valley both south and north of New Haven contains basins up to 250 m deep, for example), but it is unlikely that the deep areas on the Fall Zone surface could have been formed this way since the shape of the basins is not elongated in the direction of ice flow. More detailed mapping of the topography of the Fall Zone surface under Long Island may help resolve this problem. 

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