Hydrology & Soils Flashcards

What is the primary function of hydrology in wetland delineation?

Answer: It helps identify the presence of water, determining wetland areas

Hydrology is the most fundamental characteristic of a wetland, as it refers to the presence and movement of water. In wetland delineation, hydrology indicators (such as water marks, drift lines, or saturated soils) are crucial for determining if an area has sufficient inundation or saturation to support wetland conditions. The duration and frequency of water presence directly influence the development of hydric soils and hydrophytic vegetation, making it a primary factor in identifying wetland boundaries.

How do hydric soils contribute to wetland identification?

Answer: They help distinguish wetlands from upland areas based on soil characteristics

Hydric soils are soils that formed under conditions of saturation, flooding, or ponding long enough during the growing season to develop anaerobic conditions in the upper part. These unique soil characteristics, such as low chroma colors, redoximorphic features, or organic matter accumulation, are distinct from upland soils. Identifying hydric soils is one of the three mandatory criteria for wetland delineation, providing strong evidence of long-term wetland hydrology.

Why is the understanding of water tables essential in wetland delineation?

Answer: It helps identify the presence and duration of water saturation in wetland areas

The water table refers to the upper surface of the zone of saturation. In wetland delineation, understanding the water table's depth and duration is critical because prolonged saturation or inundation creates the anaerobic conditions necessary for hydric soils to form and for hydrophytic vegetation to thrive. Indicators of a high water table, such as water marks or saturated soil, are key evidence for establishing wetland hydrology.

How does soil permeability affect wetland delineation?

Answer: It helps identify the type of wetland by the rate of water movement through the soil

Soil permeability, or the rate at which water moves through the soil, significantly influences wetland hydrology and, consequently, wetland type. Soils with low permeability (e.g., clay) tend to retain water for longer periods, leading to prolonged saturation or ponding, characteristic of many depressional wetlands. Conversely, highly permeable soils (e.g., sand) may indicate a different hydrological regime, such as a riverine wetland with frequent but shorter inundations. This characteristic helps delineate and classify wetlands.

What is the significance of hydrophytic vegetation in wetland identification?

Answer: They provide a visual indication of water saturation and wetland conditions

Hydrophytic vegetation consists of plant species that are adapted to grow in saturated or inundated soil conditions. Their presence is a strong visual indicator that an area experiences wetland hydrology for a significant portion of the growing season. Identifying these specific plant species and their prevalence is one of the three mandatory criteria for wetland delineation, confirming the ecological conditions characteristic of wetlands.

How do precipitation and runoff influence wetland hydrology?

Answer: They contribute to the water levels and seasonal variations in wetlands

Precipitation (rain, snow) is the primary source of water for many wetlands, directly contributing to their inundation and saturation. Runoff, which is water flowing over land surfaces, also feeds wetlands, especially those in depressional areas or floodplains. Together, these processes dictate the water budget of a wetland, influencing its water levels, hydroperiod (duration of inundation), and seasonal fluctuations, which are critical aspects of wetland hydrology.

What is the role of surface water in determining wetland boundaries?

Answer: Surface water marks the boundary where wetland soils and vegetation occur

While not the sole criterion, the presence of surface water is a direct and often obvious indicator of wetland hydrology. In many cases, the edge of standing or flowing surface water can serve as a clear boundary for a wetland, as it typically corresponds with the transition to upland areas where hydric soils and hydrophytic vegetation are no longer present. It helps visually define the extent of inundation.

What is the importance of conducting soil testing in wetland delineation?

Answer: It helps confirm the presence of hydric soils necessary for wetland identification

Soil testing, specifically examining soil morphology, is crucial in wetland delineation to identify hydric soils. Delineators dig soil pits to observe characteristics like color (low chroma), redoximorphic features (mottles, concretions), and organic matter content, which are indicators of prolonged anaerobic conditions. This direct evidence confirms whether the soil meets the criteria for a wetland, distinguishing it from upland soils.

How does the Cowardin classification system classify wetlands?

Answer: By hydrology, vegetation, and substrate types

The Cowardin classification system, developed by the U.S. Fish and Wildlife Service, is a hierarchical system used to classify wetlands and deepwater habitats. It categorizes wetlands based on five major systems (e.g., Marine, Estuarine, Riverine, Lacustrine, Palustrine), which are further divided by classes, subclasses, and modifiers related to water regime, water chemistry, and special soil/vegetation characteristics. This comprehensive approach considers the dominant hydrological regime, vegetation type, and underlying substrate to provide a detailed classification.