Type 1 Wetlands: Seasonally Flooded Basins and Floodplain Forests

wetland restorationwetland types
Written By Kristin Shardlow

Although often overlooked at first glance, the seasonally flooded basin is a vital wetland ecosystem that has unique characteristics and provides essential environmental and economic services.

Seasonally Flooded Wetlands

These are a common wetland type and can be found throughout the state. As the name suggests, these wetlands typically hold water for short periods of time, typically in the spring or after heavy precipitation events. In seasonally wet years, such as in 2019, a Type 1 wetland may be waterlogged during the majority of the year. Conversely, you may not even notice it exists in seasonally dry years. Because these wetlands are dry for most of the year, they are often farmed and appear as the flooded section among row crops. In this way, Seasonally Flooded Wetlands differ from the Type 2: Wet Meadow class, as the water table in wet meadows remains higher and the soil remains saturated for longer periods of time.

Type 1 wetlands can be divided into two sub-categories; seasonally flooded basins (found in upland depressions) and floodplain forests (found along rivers and streams). 

Characteristics Specific to Type 1 Wetlands

Soil Profile: Generally composed of mineral soils (sandier textures with strata of silt and clay), these wetlands are well-drained during most of the year but can remain saturated seasonally, especially in the spring. 

Vegetation: Type 1 wetlands can host a wide range of herbaceous species as well as some woody species, although more rare. Grasses, sedges and annual plants including smartweeds, beggar ticks and wild millet can be found in seasonally flooded basins. Floodplain forests are home to more flood-tolerant tree species such as silver maple, cottonwood and American elm, with an often sparse understory populated with jewelweed, clearweed and nettles. Both cattails and reed canary grass can be found in Type 1 wetlands.

Fauna: Seasonally flooded basins and floodplain forests are key habitats for migratory waterfowl and shorebirds. Duck species utilize these wetlands as pairing ponds, and the high invertebrate populations support the dietary needs of nesting hens. Amphibian species also rely on these wetlands as critical habitat.

Four sandhill cranes in autumn, in a seasonally flooded wetland landscape.

Sandhill cranes are one of many species of migratory waterfowl and shorebirds who utilize seasonally flooded wetlands.

Functions & Benefits

As with all wetlands found in Minnesota, seasonally flooded wetlands provide a number of different ecological services and economic opportunities. Highlighted below is a list of benefits that a Type 1 wetland offers: 

Flooding/Erosion Control: Seasonally saturated basin wetlands collect runoff, reducing the likelihood of flooding and subsequent erosion in downstream, low-lying areas

Filtration & Water Quality: By collecting and storing stormwater runoff, wetlands allow for slow dispersal and percolation in neighboring, upland systems. This effectively filters excess nutrients accumulated by the water and improves overall water quality. 

Habitat & Species Diversity: As noted previously, wetlands provide habitat for rare and/or threatened species, thereby ensuring population stabilization. 

Economic Value: Activities such as waterfowl production, fur harvest, hay and forage, wild rice production, hunting and trapping leases, and selective timber can be permissible in seasonally saturated wetland areas

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Mitigation Partners, Inc. Founders Dax Dickson & Tory Christensen

Kristin Shardlow
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Type 2 Wetlands: Wet Meadows