Shrub swamps are woody wetlands dominated by shrubs (trees may cover up to 30% of the site) and are seasonally or permanently flooded with standing water for significant periods of the year. Three types of shrub swamps are recognized for Tennessee. They occur in topographic depressions. Floodplain shrub swamps are in low sloughs, swales, depressions, or channel scars within active floodplains or abandoned floodplains, but usually where flood waters and high water tables help maintain water levels. Depression shrub swamps are associated with non-alluvial depressions such as sinkhole ponds and depressions and water is supplied from rain and local runoff from the surrounding drainage area. Spring-fed shrub swamps (sometimes termed forested fens) are supplied by mineral-rich springs.