Regional supplements to the Corps of Engineers Wetland Delineation Manual
Wetland delineation remains fundamental to Corps of Engineers and Environmental Protection Agency regulatory responsibilities under Federal regulations (33 CFR 320-330), Section 404 of the Clean Water Act (CWA). Wetland delineation consists of standardized procedures for identification of wetlands and their boundaries to define the limits of Federal jurisdiction under the CWA. The Corps of Engineers Wetlands Delineation Manual historically contained indicators and methodologies for delineating wetlands. As scientists continually expand the pool of knowledge concerning wetlands, regulatory manuals should incorporate new methods, indicators, and approaches. As a result the WRTC implemented the development of ten regional supplements to the Corps of Engineers Wetlands Delineation Manual providing a vehicle for the inclusion of new and improved technical guidance for wetland delineation. The regional supplements account for provincial differences in climate, geology, soils, hydrology, plant and animal communities, and other factors impact the identification and functioning of wetlands. The regional supplements include regionalized lists of field indicators of wetland vegetation, hydrology, and hydric soils and expand procedures for problematic and difficult wetland delineations.
Regional supplement boundaries for wetland delineation
Wetland and Stream Assessment
A number of federal laws, policies, and regulations require that resource managers assess (i.e., evaluate the nature) of ecological conditions and funcitons within wetland and stream environments. The WRTC supports a variety of wetland and stream assessment approaches including the Hydrogeomorphic Approach (HGM Approach), a method capable of assessing the functional condition of an ecosystem. The approaches designed and implemented through the WRTC utilize ecosystem classification systems based on geomorphic position and hydrologic characteristics to group ecosystems into different classes (e.g., depressional, riverine, fringe wetland). Additionally, the ecosystem assessment tools developed by WRTC utilize field data in support of assessment scaling, variable selection, and application. Wetland and stream assessments are commonly used to determine current ecosystem condition, mitigation ratios, post-project impacts, and restoration success. WRTC staff also provide research in support of validating existing assessment approaches through testing assessment outcome accuracy using comparisons with field or laboratory measures. Validation measures recently examined assessment approaches in the lower Mississippi River valley and in the Appalachian region.
A recent wetland assessment guidebook developed by WRTC and validation study occurring in Appalachia
Beneficial Use of Dredge Materials
The WRTC supports wetland expansion and restoration projects through the assessment and management of wetlands created using dredge materials. These activities include monitoring of plant assemblages, soil deposition and horizon development, and faunal surveys used to determine the quality and success of dredge material wetland creation and restoration projects.
Monitoring a dredge material created island in south Louisiana
Integrated Ecological Modeling
The Integrated Ecological Modeling team made up of WRTC personnel specializes in developing modeling approaches used to answer complex environmental problems across various scales. The team focuses on understanding how critical species, including threatened and endangered species, invasive species, and species of interest (such as commercial fisheries) are impacted by changing climates, environments, and/or management actions. Ecosystems are inherently complex and consist of myriad interacting factors. Ecological modeling provides natural resource managers, planners, and environmental scientists with tools necessary to inform environmental decision-making practices. The team works with stakeholders to quickly develop scientifically-defensible approaches for informing any environmental decision making practices.
An integrated ecological model that simulates the dynamics of oyster populations in the Great Wicomico River of the Chesapeake Bay. The model integrates three models: hydrodynamics (ADH), larval transport (PTM), and population dynamics(CBOPM) to project long term sustainability of different management strategies on the oyster population.
Wetlands and Watersheds - MAWI
The Multi-Scale Assessment of Watershed Integrity (MAWI) approach assesses the integrity of riparian ecosystems and their adjacent local drainages within a watershed using a suite of indicators representing both large- and small-scale attributes and processes that influence ecosystem integrity. The hydrologic, water quality, and habitat integrity indices resulting from the baseline assessment provide a ranking of riparian ecosystem integrity within a watershed that can be easily manipulated and displayed in a GIS. The MAWI approach provides a GIS-based decision support system that integrates information and data at varying scales to produce spatially-explicit assessments on defined management concerns within a watershed. Recent applications of the approach in the western United States include the assessment of riverine ecosystem and watershed integrity. Assessment results are employed in a variety of ways, including baseline assessment and alternatives analysis. Revised assessments can be produced as updated or higher quality data becomes available. Ongoing efforts continue developing the MAWI approach for other regions.
MAWI output examining hydrologic integrity (ERDC-Coastal Hydraulics Laboratory)
Identification of altered and problematic wetlands
WRTC staff frequently aid USACE Districts, the EPA, and other agencies in the identification and delineation of altered and problematic wetlands throughout the United States. Altered wetlands include areas subject to fill placement, drainage, agriculture/silviculture, and other human activities resulting in disturbances that make wetland identification difficult. Recent WRTC projects examined altered wetlands exposed to fill materials within floodplains and areas subjected to long term hydrologic modification (e.g., drainage, irrigation). Problematic wetlands include areas that are hard to identify due to a natural feature affecting the presence of indicators of wetland hydrology, hydric soils, or hydrophytic plants. WRTC staff recently examined problematic wetlands throughout the upper Midwest exhibiting red parent materials, marl soils, and high chroma sandy soils. These projects often utilize technologies including Indicator of Reduction in Soil (IRIS) tubes, groundwater monitoring and modeling, alpha-alpha dipyridyl dye and the application of the Corps of Engineers Technical Standard for Water-Table Monitoring of Potential Wetland Sites and the Technical Standard for Hydric Soils. Study results often lead to development of new guidance for wetland delineators in the affected region.
Groundwater monitoring equipment and IRIS tubes installed in problematic wetland (left) and upland (right) locations
Investigation of permafrost hydric soil vegetation characteristics in Alaska
As part of an effort to improve permafrost mapping capabilities and promote installation infrastructure longevity, WRTC staff examined permafrost soils across wetland transects located near Fairbanks, AK. Measurements included hydric soil descriptions, determinations of soil moisture, depth to permafrost and carbon and nitrogen content. Additionally, inventories of floral communities provided data on changes in vegetative cover within areas exhibiting polygonal/patterned ground features commonly associated with permafrost. The collected data allowed for the establishment of relationships between soil parameters and plant cover types. Future work will incorporate measures of plant photosynthesis, remote sensing data, subsurface resistivity, and ground penetrating radar.
Permafrost soil (left) and landscape (right) photos from data collection in interior Alaska