The history of Richardson Bay and DeSilva Island in particular, is one of change wrought by human activity in the Bay and along its shoreline. Construction of the railroad in 1883 was probably the first major event that reconfigured the western - i.e. Mill Valley and Tamalpais Valley - shoreline of the Bay.

It served as a partial levee, separating island marshes from the waters of the Bay. DeSilva Island remained an island, linked at low tide to the Strawberry mainland by salt marsh and exposed mudflat. More defining than construction of the railroad was the filling of the Bay for construction of the "new" Highway 101. The effect of this, beyond its obvious advantage to auto transport through Southern Marin, was to fully link DeSilva Island to the "mainland" and to sever the high-tide connection around the island that merged with waters of Mill Valley marshes and shoreline. The results were the reconfiguration of DeSilva Island as a peninsula, the formation of a lagoon on the East side of 101 that came to be known as "Belloch Lagoon", and the isolation from the Bay of a small triangular salt marsh west of 101 commonly known as "Goodman Marsh."

The infill for Highway 101 also created building sites for future commercial development along the Highway: Strawberry shopping center and eventually the service stations and food outlets near Seminary Drive and DeSilva Island. An unintended consequence of placing the weight of fill over the underlying bay mud was to displace a volume of soil into Belloch Lagoon - termed a "mud wave" - creating a small elevated mound within the lagoon that was above the reach of even the highest tides. This also impaired tidal circulation in the vicinity of the mound. The opportunity to mitigate the problem came later when, in constructing an entry road to serve future development on DeSilva Island, it was necessary to fill a culvert and an area of wetland. The obvious mitigation was to undo the mud wave, that is, to restore all or part of the mound to elevations more susceptible to regular tidal inundation and, at the same time, improve tidal circulation to back areas of the lagoon salt marsh. In addition, the shoreline itself, which had suffered the neglect and abuse common in natural resource areas backed by commercial uses, could be cleaned of trash, landscaped, and opened to appropriate pedestrian access.

Belloch Lagoon is actually an extension of Strawberry Cove, itself an extension of Richardson Bay southeast of DeSilva Island. It is like many lagoons, typically shallow bodies of water that lie parallel or adjacent to a coastline, in this case the shoreline of Richardson Bay and greater San Francisco Bay. Lagoons are bodies of relatively quiet water, often with restricted tidal flow and higher than normal (for the Bay) rates of sediment deposition. Silt carried in by in-flowing tide is deposited around rocks or plants on the slowly ebbing tide. Beginning as an unvegitated mudflat when Highway 101 cut it off from other waters to the west, Belloch Lagoon provided a fairly stable environment for organisms, including plant fragments and seeds, to establish in the mud, removed from the turbulent effects of wind, waves , and tides in the more exposed Bay. As plants became established, siltation increased. Over time the majority of the lagoon has become almost fully covered by typical salt marsh vegetation, notably cordgrass (Spartina foliosa) and pickleweed (Salicornia pacifica). Located as they were close to the rich shellfish beds of Richardson Bay, both Strawberry peninsula and DeSilva Island were attractive upland sites for Miwok habitation. The biological resources also attracted resident, migrating, and wintering shorebirds and waterfowl, and continue to offer refuge to diverse avian populations, such as the great blue herons that nest on DeSilva.

Written by Nona Dennis