25 Jul 2024

Regeneration Dynamics of Bottomland Hardwood Sites Following Prolonged Growing-Season Inundation

Abstract: The spring flood of the Mississippi River and backwater areas in 2019 resulted in large-scale flooding and was the longest-lasting flood event since the Great Flood of 1927. This flood event provided a rare opportunity to establish permanent plots in batture and backwater habitats to evaluate forest-stand dynamics following prolonged flooding. In this study, we evaluated postflooding conditions of forest overstory, midstory, and regeneration by establishing permanent plots at four locations subjected to varying amounts of flooding within the Mississippi River batture and the Yazoo–Mississippi Delta backwater region. Our results highlight oak regeneration success following the 2019 flood event as well as the utility and need to establish and monitor permanent plots to increase our understanding of floodplain forest dynamics in regions experiencing prolonged riverine flooding during the growing season.

11 Sep 2023

Selection of a Time Series of Beneficial Use Wetland Creation Sites in the Sabine National Wildlife Refuge for Use in Restoration Trajectory Development

PURPOSE: The development of regional restoration trajectories of marsh creation and nourishment projects is key to improved design, management, and implementation of adaptive management principles. Synthesizing information from multiple marsh creation projects constructed at various times but with consistent site characteristics and borrow material sources, helps elucidate restoration success in a specific region. Specifically, this technical note (TN) documents the process of determining a suitable study area, construction methods, and the current state of establishing sites in the Louisiana Gulf Coast that could be used for restoration trajectory development. This investigation compiled information from the construction phases, Landset 8 satellite imagery, and the most recent digital elevation model (DEM) to investigate elevation and vegetation establishment within these sites.

27 Apr 2023

Technical Guide for the Development, Evaluation, and Modification of Wetland Rapid Assessment Methods for the Corps Regulatory Program

Abstract: The US Army Corps of Engineers (Corps) Regulatory Program considers the loss (decrease) and gain (improvement) of wetland functions as part of Clean Water Act Section 404 permitting and compensatory mitigation decisions. To better inform this regulatory decision-making, the Regulatory program needs accurate, transparent, objective, and defensible approaches to assess the function and condition of wetlands. Additionally, wetland assessments must balance the need for objective decision-making with the concurrent need to make Regulatory program decisions in a timely manner. Consequently, it is often necessary to assess wetlands using rapidly attainable proxy measures of ecological function or condition by evaluating a suite of metrics that represent structural and compositional attributes of a wetland. In response, this document describes a set of guidelines to effectively develop, evaluate, and modify wetland assessment methods, specifically for the Corps Regulatory Program.

1 Dec 2022

A Review of Tidal Embayment Shoaling Mechanisms in the Context of Future Wetland Placement

Abstract: Wetland construction in tidally influenced embayments is a strategy for beneficial use of sediment dredged from nearby navigation channels. These projects have the potential to alter basin morphology, tidal hydrodynamics, and shoaling trends. This special report provides a broad review of the literature related to engineering-induced changes in tidal range, salinity, tidal prism, tidal asymmetry, and other known causes of shoaling. Each potential shoaling mechanism is then evaluated in the context of wetland placement to provide a foundation for future beneficial use research. Based on a compilation of worldwide examples, wetland placement may reduce tidal amplitude and enhance ebb current dominance, thus reducing shoaling rates in the channels. However, constructed wetlands could also reduce the embayment’s tidal prism and cause accelerated shoaling relative to the pre-engineered rate. Because constructed wetlands are often created in conjunction with navigation channel dredging, the system’s morphologic response to wetland construction is likely to be superimposed upon its response to channel deepening, and the net effect may vary depending on a variety of system- specific parameters. Planning for future wetland placements should include an evaluation of local hydrodynamic behavior considering these factors to predict site-specific response.

29 Aug 2022

Financing Natural Infrastructure: South Bay Salt Pond Restoration Project, California

PURPOSE: This technical note is part of a series collaboratively produced by the US Army Corps of Engineers (USACE)–Institute for Water Resources (IWR) and the US Army Engineer Research and Development Center (ERDC). It describes the funding and financing process for the South Bay Salt Pond Restoration Project in San Francisco Bay, California and, like the other technical notes in this series, documents successful examples of funding natural infrastructure projects. The research effort is a collaboration between the Engineering With Nature® (EWN®) and Systems Approach to Geomorphic Engineering (SAGE) programs of USACE. A key need for greater application of natural infrastructure approaches is information about obtaining funds to scope, design, construct, monitor, and adaptively manage these projects. As natural infrastructure techniques vary widely by location, purpose, and scale, there is no standard process for securing funds. The goal of this series is to share lessons learned about a variety of funding and financing methods to increase the implementation of natural infrastructure projects.

29 Sep 2021

Inundation Depth and Duration Impacts on Wetland Soils and Vegetation: State of Knowledge

Abstract: The following synthesizes studies investigating plant and soil responses to increased inundation in order to support ecosystem restoration efforts related to the alteration of natural wetland hydrodynamics. Specific topics include hydrologic regimes, soil response to inundation, and implications for vegetation communities exposed to increased water depths. Results highlight the important interactions between water, soils, and vegetation that determine the trajectory and fate of wetland ecosystems, including the development of feedback loops related to marsh degradation and subsidence. This report then discusses the knowledge gaps related to implications of inundation depth, timing, and duration within an ecosystem restoration context, identifying opportunities for future research while providing source materials for practitioners developing restoration projects.

27 Sep 2021

An Evaluation of Soil Phosphorus Storage Capacity (SPSC) at Proposed Wetland Restoration Locations in the Western Lake Erie Basin

Abstract: Historical loss of wetlands coupled with excess phosphorus (P) loading at watershed scales have degraded water quality in portions of the western Lake Erie Basin (WLEB). In response, efforts are underway to restore wetlands and decrease P loading to surface waters. Because wetlands have a finite capacity to retain P, researchers have developed techniques to determine whether wetlands function as P sources or sinks. The following technical report evaluates the soil P storage capacity (SPSC) at locations under consideration for wetland restoration in collaboration with the Great Lakes Restoration Initiative (GLRI) and the H2Ohio initiative. Results indicate that the examined soils display a range of P retention capacities, reflecting historic land-use patterns and management regimes. However, the majority of study locations exhibited some capacity to sequester additional P. The analysis supports development of rankings and comparative analyses of areas within a specific land parcel, informing management through design, avoidance, removal, or remediation of potential legacy P sources. Additionally, the approaches described herein support relative comparisons between multiple potential wetland development properties. These results, in conjunction with other data sources, can be used to target, prioritize, justify, and improve decision-making for wetland management activities in the WLEB.

12 Aug 2021

Quantifying Functional Increases Across a Large-Scale Wetland Restoration Chronosequence

Abstract: Over 300,000 ha of forested wetlands have undergone restoration within the Mississippi Alluvial Valley region. Restored forest successional stage varies, providing opportunities to document wetland functional increases across a large-scale restoration chronosequence using the Hydrogeomorphic (HGM) approach. Results from >600 restored study sites spanning a 25-year chronosequence indicate that: 1) wetland functional assessment variables increased toward reference conditions; 2) restored wetlands generally follow expected recovery trajectories; and 3) wetland functions display significant improvements across the restoration chronosequence. A functional lag between restored areas and mature reference wetlands persists in most instances. However, a subset of restored sites have attained mature reference wetland conditions in areas approaching or exceeding tree diameter and canopy closure thresholds. Study results highlight the importance of site selection and the benefits of evaluating a suite of wetland functions in order to identify appropriate restoration success milestones and design monitoring programs. For example, wetland functions associated with detention of precipitation (a largely physical process) rapidly increased under post restoration conditions, while improvements in wetland habitat functions (associated with forest establishment and maturation) required additional time. As the wetland science community transitions towards larger scale restoration efforts, effectively quantifying restoration functional improvements will become increasingly important.

1 Oct 2020

Evaluating Soil Phosphorus Storage Capacity in Constructed Wetlands: Sampling and Analysis Protocol for Site Selection

Abstract: Soil characteristics determine the capacity of wetlands to sequester phosphorus (P). However, researchers have not yet developed a standard protocol for conducting soil sampling to document the soil phosphorus storage capacity (SPSC) for constructed wetland site selection. In response, the following technical note provides step-by-step instructions for selecting soil sample locations, describing site conditions, conducting soil sampling, and preparing samples for laboratory analysis. This note also includes calculations and interpretation of SPSC.

9 Jul 2020

PUBLICATION NOTICE: Hydrodynamics of a Recently Restored Coastal Wetland: Hamilton Wetlands, California

Abstract: Hamilton Wetlands is a recently restored tidally influenced basin located along the northwest coast of San Pablo Bay, California. Instruments to measure waves, currents, and wind were deployed for a period of up to 2 years shortly after tidal flow was re-introduced to the wetland to examine the sediment and hydrodynamic response. The results indicate that local re-suspension is relatively rare owing to the weak interior tidal currents and the limited fetch within the 3 km long basin. Asymmetries in the acoustic backscatter intensity combined with the much higher flow speeds measured at the entrance suggest a net import of fine sediment. The basin also experiences a distinct seasonal variation that likely contributes to sediment re-distribution. During the summer months, higher wind speeds correlate with turbidity suggesting local re-suspension of fines that are distributed by winds. Overall, the measurements suggest that the sediment dynamics in this shallow water system are controlled by two main factors: (1) net sediment import through the inlet entrance and (2) mixing of interior sediment through a combination of intermittent wind and wave stirring.