Morphology Change Validation of Shark River Inlet

UNDER CONSTRUCTION

Shark River Inlet, located on the north New Jersey coast, is served by a federal navigation channel that has until recently required little maintenance dredging. Although possessing a small estuary, the inlet is hydraulically efficient because of the small width to depth ratio of its entrance that is stabilized by parallel jetties. After placement of approximately 4.8 million cubic meters of beach nourishment to the north and south of the inlet as part of an erosion-control project conducted in the late 1990s, inlet maintenance increased beyond that anticipated. The Coastal Modeling System (CMS) was established to numerically simulate waves, current, sand transport, and morphology change.

Model Setup

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Figure 3. Telescoping Grid.

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Figure 4. Zoom in of telescoping grid over the backbay (note the detail of tidal creeks).

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Figure 5. Example of ebbing currents exiting the inlet.

The Non-equilibrium Transport (NET) method also controls the capacity of sediment transport through scaling factors such as adaptation lengths or times, generally dependent upon length-scales of morphologic features such as bedforms or timescales of sediment movement. As a total load formulation is used with the NET, the Adaptation Length must be modified to calibrate to morphology. The Adaptation Length is a length scaling factor that is typically based on localized bedforms. The smaller the Adaptation Length, the closer the model is to Equilibrium Transport which results in greater rates of transport that is more localized. Adaptation Lengths tested included 1, 2, 3, 4, 5, 10, and 100 meters. An Adaptation Length of 3 meters was selected for the entire domain of the final calculations because of the realistic patterns and trends observed in the calculations as compared to the measurements. Final parameter values were chosen to produce calibration of results to specific regions of interest, such as channel infilling in the dredged pit.

Table 1. Sediment transport and morphology parameters in the CMS

Parameter	Value
Formulation	Advection-Diffusion
Sediment Transport Formula	Van Rijn
Bed Load Scaling Factor	1.0
Suspended Load Scaling Factor	1.0
Sediment Porosity	0.4
Bed Slope Coefficient	0.1
Morphologic Acceleration Factor	1.0
Total Load Adaptation Length Method	Constant
Adaptation Length	1.0

Validation

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Figure 5. Comparison of Measured 2005 Pre-Dredging Bathymetry with Calculated 2005 Pre-Dredging Bathymetry.

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Figure 6. Comparison of A) Measured Bathymetry with B) Calculated Bathymetry.

Table 2. Measured and calculated volume change of parts of the ebb shoal

Dredged Channel	Remainder of Ebb Shoal
Measured = _,000 cy	Measured = _,000 cy
Calculated = _,000 cy	Calculated = _,500 cy
_ % Difference	_ % Difference

Discussion

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• For a definition of the goodness of fit statistics see Goodness of fit statistics

References

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