National Park Service, Cape Cod National Seashore, 99 Marconi Site Road, Wellfleet, MA 02667

A -- HYDRODYNAMIC AND SEDIMENTATION MODELING FOR ESTUARINE HABITAT RESTORATION AT HERRING RIVER, WELLFLEET, MA SOL 1443-RFQ1730-9-294 POC Colina Rivetts, Contract Specialist, Cape Cod National Seashore, 99 Marconi Site Road, Wellfleet, MA 02667. (508) 349-3785, ext. 225. Requests for quote package may be made by mail, email, or fax (508) 349-9052. E-MAIL: Contract Specialist, Cape Cod National Seashore, colina_rivetts@nps.gov. Request for Quotations (RFQ) to be issued in early November requesting proposals for the following research project. As part of a Park-wide program of salt marsh restoration, CACO managers, the public and local and state environmental authorities have renewed interest in restoring estuarine habitats at Herring River. The overall approach is to describe the present physical system, i.e. tidal regime, freshwater discharge, and topography including the creek system impediments to surface flow, and then to model an hydrologically restored estuary, i.e. with tidal restrictions reduced or eliminated. Tasks include preparation of a detailed plan and (1) The collection of detailed topographic data for the entire 600-ha flood plain (elevations < 3 m-NGVD) above the Chequesset Neck Dike within CACO and including the Mill Creek tributary. The modeling requires detailed topography (e.g. 5 cm vertical resolution): (a) to compute flood plain volumes for prediction of tide heights, (b) to estimate flooding extent,depth and duration through tidal cycles, (c) to estimate ebb and flood tide velocities and effects on erosion and accretion both within creeks and on the marsh plain, and (d) to identify sensitive structures that may experience flooding. (2) Numerical modeling of tide heights and salinities based on, and encompassing the area of, detailed topography. New models will incorporate updated tide height and newly-refined topographic data and, as with Roman (1987), will show the effects of a range of alternative levels of increase in tidal prism. Predicted tide heights will be compared to the elevations of road grades, spoil piles and other structures within the flood plain to suggest management actions which optimize estuarine restoration and avoid social conflicts. (3) An assessment of hydrography after tidal restoration, including digitized mapping of principal tidal creeks, expected flood- and ebb-tide velocities and the likely areal extent and rate of sediment deposition both in creeks and on the wetland proper. Modeling will produce estimates of the flow velocities throughout the normal tidal cycle and during storms for various levels of tidal restoration. Sediment transport and deposition will be assessed from model-predicted flow velocities and from the grain sizes of sediment within the tidal channels. (4) Investigators will produce recommendations for: (a) the optimum rate of increase in tidal flow given historic subsidence, the predicted rate of sediment accretion, and ecological constraints on hydroperiod; (b) tide height monitoring and physical adjustments to tidal flow during the restoration process to ensure that high tide heights do not exceed the accretion capacity of the subsided wetland; (c) the need for the removal of structures to maximize habitat restoration; (d) the need to re-establish original creek meanders to achieve more natural hydrography; (e) the need to actively compensate for subsidence by transferring sediment from tidal creeks and elsewhere to the wetland surface; (f) management actions to reduce the effects of increased tide heights on two homes and a golf course within the flood plain. This is set aside for small business. All requests for packages must be made by mail to the above address or via email or via fax to (508) 349-9052. Project estimate is between $25,000 and $100,000. Anticipated issue date for Request for Quotations is 11/06/98 with a response date of 12/04/98. Posted 10/22/98 (W-SN264464). (0295)

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