Hydrology indicators Wetland hydrology refers to the presence of water at or above the soil surface for a sufficient period of the year to significantly influence the plant types and soils that occur in the area. Although the most reliable evidence of wetland hydrology may be provided by gaging station or groundwater well data, such information is limited for most areas and, when available, requires analysis by trained individuals. Thus, most hydrologic indicators are those that can be observed during field inspection. Most do not reveal either the frequency, timing, or duration of flooding or the soil saturation. Soil is waterlogged during the growing season.
Water marks are present on trees or other erect objet.
Such marks indicate that water periodically covers the area to the depth shown on the objects. Drift lines, which are small piles of debris oriented in the direction of water movement through an area, are present. These often occur along contours and represent the approximate extent of flooding in an area. Debris is lodged in trees or piled against other object by water. Thin layers of sediments are deposited on leaves or other objects.