The securing of a federal grant last month to restore three coastal wetlands in Suffolk County is the start of a lengthy process to make sure the work doesn't do as much harm as good.

The selection of the sites — Cupsogue Beach Marsh, Scully Marsh and the East Islip Preserve — and securing of funding represent years of advance work, including collecting data on tidal flooding, risk assessments and a cost-benefit analysis. The cost of restoring Cupsogue, for example, is estimated at $2 million, with losses averted totaling $50.6 million.