Coastal and subcoastal saline swamp

Coastal and subcoastal saline swamp – Hydrology

• Wet
• Dry

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Saline swamps are seasonally inundated with fresh water but become more brackish as they dry. These habitats can be seasonally flooded with water and dry out completely before the next season's rain.

Water inputs

The hydrology of a wetland habitat is related to a site’s topography, substrate type and position within the catchment. Climatic factors (especially those related to rainfall) also play a significant role in the regularity, seasonality, duration and amount of water entering and leaving the wetland.

Floodplain wetlands can be flushed with water from overbank flow, streams leading directly to the site, sheet flow across the floodplain, rainfall, run-off from the local watershed, hyporheic flow and other groundwater discharge, or a combination of these sources.

If groundwater table levels and substrate permeability permit, this can lead to more constant systems. This wetland habitat type can play a role in groundwater recharge/discharge.

If the wetland is not part of the floodplain (a non-floodplain depressional system), its dominant water sources are rainfall, run-off from its local water shed and groundwater (if water table levels and substrate permeability permit).

Water outputs

Evaporation, transpiration and groundwater recharge can lead these systems to dry out, often completely (see dry model).

For floodplain systems overbank floods move out onto the floodplain or back to the channel, connecting the wetland habitat to other wetland habitats in the floodplain. Water may also flow out to the ocean via distributary channels, depending on topography.

Other hydrological information

This wetland habitat type is typically found on flat landscapes and therefore tends to experience a slow flow rate of water movement and only a limited capacity to retain any great depth of water. Inundation is usually temporary for all but the deepest parts of the wetland habitat, ranging from a few weeks each year during periods of heavy rain and flash flooding, to many months. In some cases, the wetlands may dry out only for a short period in the dry season or may remain wet in the innermost parts.

Though these wetlands are above Highest Astronomical Tide (HAT) and therefore are not estuarine, they still receive some ocean-derived salt influence from their close proximity to marine and estuarine systems—from wind action, unusually high tides from storm surges and/or as a result of their position on old marine plains. This salinity typically decreases with distance from marine and estuarine systems.

Last updated: 22 March 2013