Area Map

The Oslo Management Area's (OMA) northern boundary is located at the 17th Street Bridge in Indian River County (IRC) and extends south for approximately 11.5 miles to the northern portion of St. Lucie County (SLC). OMA includes marshes on both the eastern and western shores of the Indian River Lagoon (IRL), and islands within the lagoon. 22 impoundments occur in this Management Area. While most of these impoundments are privately owned, 2 are publicly owned with at least 2 more currently under serious consideration for public purchase.

NOTABLE FEATURES WITHIN OMA. As is the case with many of the 10 Management Areas, the fact that many of the OMA marshes are privately owned has limited optimal management opportunities in this area. Most of the marsh property is impounded with several of the impoundments under RIM management. The southern end of the OMA is near the Ft. Pierce Inlet which provides good oceanic water exchange especially for the St. Lucie County impoundments in the southern end of OMA. IRC's South Relief Canal (near the northern end of OMA) provides periodic freshwater pulses to the IRL.

IRC Impoundment #12 (located on the barrier island at the IRC/SLC border) and SLC Impoundments #23 & 24 served as study sites for the series of Coastal Zone Management studies during the 1980's which studied ecosystem effects of impoundment management practices. This research demonstrated the scientific validity of Rotational Impoundment Management (RIM) as a viable impoundment management technique providing source reduction mosquito control with natural resource benefits.

It is noteworthy that a joint purchase of 300 acres on the mainland side of the lagoon in and around IRC Impoundment #18 (Vista Royale) by IRC and the St. Johns River Water Management District is playing an important role in preserving and improving management of these resources which include an oak hammock, scrub hammock, tidal and impounded wetlands. A grant awarded by the Florida Inland Navigation District (FIND) will allow development of the educational opportunities for this area which is being called the "Oslo Riverfront Park".

Several miles south of Oslo Road in SLC, occurs several marshes which receive a considerable fresh water input from the uplands, in particular the sand ridge. Also along the west side of US 1 lies the "Savannahs", a freshwater habitat targeted for public acquisition.

On the eastern edge of the lagoon in SLC Impoundment #23 (which is State owned) abuts a large oak-palmetto hammock with considerable encroachment by exotic vegetation in particular Brazilian pepper (Schinus terebinthifolius). Several miles south of this lies Impoundment #19B which includes a fairly intact tropical hammock.

Vegetation in OMA impoundments differ considerably among marshes. In some impoundments, Avicennia germinans (black mangrove), Rhizophora mangle (red mangrove), Laguncularia racemosa (white mangrove), or a combination of these dominate, while in some other marshes, Batis maritima, or Salicornia spp. dominate. Several rookeries influence bird use in OMA. One is adjacent (but just outside) OMA to the north, the other is a spoil island off Oslo Road, the third within IRC Impoundment #13.

INDIAN RIVER COUNTY COMPONENT OF THE OMA. In IRC, OMA includes 13 impoundments totalling 779 acres with only Impoundment #17 (=133 acres) being publicly owned. Also included are approximately 150 acres of unimpounded marsh divided among the lagoon fringes and islands within the IRL.

IMPOUNDMENTS. The 13 OMA impoundments in IRC are currently managed in a variety of ways including: 1) Rotational Impoundment Management (RIM), 2) summer flooding only, 3) breached with larvicide treatments as necessary, 4) connected to the lagoon through culverts, 5) year-round flooding, 6) receiving secondarily treated wastewater (the only example we are aware of along the IRL; the possible impacts of this practice are unclear).

UNIMPOUNDED MARSHES. The unimpounded IRC marshes within OMA include marshes fringing the lagoon and several islands. The largest unimpounded marsh is where the South Relief Canal enters the IRL.

ST. LUCIE COUNTY COMPONENT OF OMA.

IMPOUNDMENTS. Impoundments 23, 24, 19B, 19D, and 21 are primarily estuarine systems managed in a variety of ways, including RIM, tidal trapping, or breached. Larviciding is done frequently, especially in impoundments 23 and 24. Impoundments 23 and 24 are frequently used by wading birds, and 19B is very alluring to wading birds during summer drawdowns. These impoundments contain large stands of mangroves and saltwort.

Impoundments 14A, 14B, and 14C are basically fresh water systems with little or no connection to the lagoon. These marshes maintain a variety of fresh water fauna and flora, and provide forage and resting areas for mottled ducks, blue-wing teal, and a variety of wading birds. Water is provided to these marshes via rainfall, or by runoff and seepage from the coastal ridge system immediately to the west. A nearly pristine coastal hammock lies to the west of impoundment 14C.