Marsh Trail Guide
Habitats of the Upper Texas Coast
The prairie, tidal marsh, and riparian forests here are some of the last examples of such habitats in the area. These habitats dominated the coastal plain 200 years ago. But fire suppression, exotic species, ground subsidence (due to groundwater pumping) and development have altered much of the landscape.
About the trail
The trail starts at the parking lot on the north side of the San Jacinto Monument. The prairie portion of the trail is asphalt and extends 700 feet to the edge of the marsh. Look for a rest area under the canopy of several large oak trees. At the marsh, step onto the 510-foot boardwalk to experience the tidal marsh firsthand. The boardwalk crosses both dense marsh and open water. Past the boardwalk, a natural surface trail winds through a forested area.
Little bluestem, big bluestem, Indiangrass, and switchgrass at one time dominated the native coastal tall grass prairie. Today, less than 1 percent of the original coastal prairie remains. Many species of wildlife which depend on the grasslands are gone from the area. These include the Attwater’s prairie chicken, black-tailed jackrabbit, Texas horned lizard, American bison and many songbirds.
Three factors led to the demise of the prairie:
- Suppression of natural fires
- The spread of exotic species, especially the Chinese tallow (a tree)
- Use of the land for agriculture or developments.
In 1836, most of the battlefield was open prairie. A band of trees lined the bluff overlooking the marsh and the nearby Boggy Bayou. Three small islands of trees called “mottes” grew in the battlefield. Soldiers fought in grass "as tall as a horse's belly."
As you approach the boardwalk, you travel from uplands to wetlands. On the right, look for a small patch of bunched grass that is different from both the grass of the prairie and the grass of the open marsh. This is gulf coast cord grass, which dominates a unique habitat called high marsh. Saltwater occasionally floods high marsh in the spring and fall. By contrast, the high tide floods the marsh hay and smooth cordgrass found in the low marsh further along the boardwalk every day.
At one time, many tens of thousands of acres of cordgrass marshes lined the coves, flats, channels, and floodplains of the Galveston Bay system.
Most of the marsh at San Jacinto was buried under 5 to 10 feet of mud and sand dredged from the San Jacinto River to widen and deepen the shipping channel. Later, subsidence lowered the land. By the 1980s, this area was open water.
Pumping large amounts of groundwater can lead to subsidence. The land actually sinks, or subsides. Industrial water pumping here led to subsidence. The marsh and the area around the reflecting pool sit below sea level today. A dike and frequent pumping keep the battleground dry.
Tidal marshes are very important for wildlife and play a role in the life cycle of seafood species like shrimp, crabs, spotted weakfish, red drum, and flounder.
Many species of shorebirds, wading birds, and resident and migratory waterfowl also depend on the marshes. They also absorb and otherwise destroy pollutants and moderate floodwaters, so there was a need to restore them.
Clean sand and sediment from the adjacent San Jacinto River were pumped into the area in the 1990s to recreate the marsh present today. We continue to work on restoring all of the tidal wetlands at San Jacinto.
You might see a river otter and a diamondback terrapin in the marsh. Keep an eye out for the cottonmouth, also known as the water moccasin, a venomous snake and common predator at San Jacinto.
As the coastal rivers meander back and forth, they leave behind terraces and floodplains of marshes, swamps and hardwood forests. These forests dissect the coastal prairies and add to the diversity of the ecosystem. They provide homes and critical foraging habitat to many species of resident and migratory wildlife.
Logging and channelization for flood control have reduced the forests to a small fraction of their original area. At the east end of the San Jacinto site, you will find a small remnant forest, with some mature trees three feet in diameter.
Across the marsh from the trail, a younger forest has sprung up on dredged soils deposited throughout the 20th century. This diverse forest grew from seeds which floated down from upstream forests during floods.
Take a moment to stop and look around you. Note that the trees form a dense canopy. This canopy provides many of the same biological benefits as a more mature forest’s canopy.
The construction of this interpretive trail was made possible by a Coastal Management Program grant through the Texas General Land Office, along with grants from the U.S. Fish and Wildlife Service, Galveston Bay Estuary Program (NOAA,) and the National Fish and Wildlife Foundation. Partners include: the Texas Department of Transportation, Telephone Pioneers of Texas, Environmental Institute of Houston, and Harris County Adult Probation Office. Future plans call for additional grant funding that will allow the trail to be extended another 500 feet into the forest.