Tidal Marsh

This broad expanse of tall salt grass lines a river running toward a coast with unusually high tide range. Only partly hidden below the grass is an expanse of fine, grey mud that has collected here. At high tide salt water entirely covers this surface, but at low tide it is revealed as a high platform standing several yards/meters above river level.

Dimensions Many parts of this salt marsh extend more than a hundred yards/meters between more solid ground and open water. The elevation difference here between high and low tide is typically 22-36 ft (7-11 m).

Key Details

The stalks and roots of salt grass have trapped sediment from the estuary's mud-charged tidal flows, building up the salt marsh surface to near high tide level. The outer edge of the marsh continues to collect mud and grow further into the water by several yards/meters per year.
The extreme tides here rise and fall twice in a 24 hour period. Successive high and low tide levels don't quite match up in the same day: the second high tide, for example, may be six or seven feet (2 m) higher or lower than the first.
The surface of the marsh is mostly flat, but there are some more inshore areas and isolated mounds that are elevated by a foot or two (half meter), with steep storm-wave-eroded edges, giving a stepped appearance. As winter ice breaks up on the marsh surface, patches of frozen-in mud and grass rip away from the ground, drift with the ice to other places in the marsh, and are left on the surface by melting. These deposits make up the mounds, and places they were recently torn from are seen as shallow depressions of the marsh surface, with new grass and possibly some saltwater pools persisting at low tide.
Small grass-free channels aid salt water evacuation of the marsh surface as the tide ebbs. Larger streams coming from inland cut deep, open troughs that act as 'express routes' for tidal flow, and therefore complicate the directions of marsh surface flooding and runoff during seawater invasion and retreat.
The grass blades here are tough and abrasive-edged. Exploring here is best done in high boots or waders, jeans and long-sleeved shirts or coats.
With every step, boots sink a few inches (several centimeters) into the mud, and release with a sucking sound. Unlike a mud patch on typically found on dry land, this water-logged silt and clay is several yards/meters deep. For someone continuing to stand in the same spot, the sinking does not stop, but continues slowly without abating. A ten-minute pause can nearly bury and trap boots; people inattentively stopping in the same spot for half an hour may find themselves thigh-deep in mud.
The smoothness of mud at the base of the grass contributes to an impression of barren ground here. However this ground is visited by many sea and shore creatures through the day. Many permanent residents live buried in the mud, including mollusks and marine worms. Salt marshes are important feeding areas for migratory fish and birds.

Story Elements

While the grassy surface of the tidal marsh appears stable and peaceful, the slopes of bare mud exposed at low tide give a strong sense of disruption to the scene.
Local residents will visit the salt marsh periodically to dig clams, collect crabs, and do other foraging.
Shallow-draft boats can navigate the marsh freely during brief hours of high tide, but will be stranded in a sea of grass and mud for most of the day. Grass is tall enough here to hide a stranded rowboat from distant view, especially with camouflage of a few tufts of cut grass.
A person staying still in one spot, distracted by work or reverie, may become trapped by sinking two or three feet into the mud. For rescue, a slow, steady extraction is needed to allow for slow shifting of the mud and avoid injury. One or two people standing next to the trapped person, pulling them up, will sink down at least as fast. What is needed is a hold on a broader solid platform or a rope attached to a solid object on distant firm ground with the trapped person or others exerting consistent pull. Helpers with shovels might also need to rapidly but carefully dig mud out from around the person's legs, especially if rising tide makes time for rescue short.
A person needing to hide out in the marsh, staying still, can avoid sinking much by lying down flat on the mud surface. This situation may be accompanied by some close-up wildlife encounters: crabs or field mice moving through the grass stems, landing of a large flock of migratory birds, or even fish brushing by as the marsh surface begins to flood.
Combat Dynamics:
- People familiar with this terrain will have tremendous advantage over invaders on foot, especially if they can maneuver to keep them stalled on the marsh surface.
- Heavy vehicles unwisely taken onto the marsh surface will quickly become fixed in place.
- Sharpshooters on the marsh surface can get reasonable cover by kneeling, but will need to regularly shift position, possibly flailing while pulling knees and feet out of the mud. Motion of the salt grass tops will give away their positions, even if they are fully out of sight.
- A hand-to-hand fight scene will be accompanied by novel wet thuds and sucking sounds as fighters shift feet on the mud, and swishing sounds as they barge through the grass. Weapons pushed forcefully into the mud will require extra force, and possibly seconds, to extract. s shift feet

Reference Location

Salt marsh in St. Croix River estuary draining to the Bay of Fundy, near Windsor, west-central Nova Scotia.