14 May 2021

Remotely Sensed Habitat Assessment of Bottomland Hardwood and Swamp Habitat: West Shore Lake Pontchartrain Hurricane Storm Damage Risk Reduction System Potential Impact Area

Purpose: This study used remote sensing techniques to identify and assess the current condition of bottomland hardwood (BLH) and swamp habitats within the West Shore Lake Pontchartrain (WSLP) hurricane storm-damage risk reduction system (HSDRRS) project area. This effort provides baseline knowledge of the location and quality of these habitats prior to the construction of the WSLP HSDRRS project. The resultant products will assist the USACE—New Orleans District (MVN) by informing ecosystem decision-making related to environmental assessments.

24 Sep 2020

Readily Available Hydrologic Models: Pertinence to Regulatory Application

Purpose: Water is the driving force of wetlands. Hydroperiod represents both the frequency and duration of inundation or soil saturation whether it is from flooding or ponding. The formation of hydric soils and an expression of hydrophytic vegetation are evidence of the hydroperiod, which can be described along a gradient of hydrologic conditions (Figure 1). Hydrologic modeling provides a means to establish wetland hydroperiod, including current wetland hydrologic conditions and forecasting future conditions in response to future with and without wetland impacts or restoration actions. Today, fast computer processing and hydrologic models allow the user to make a large number of computations very rapidly on potentially large volumes of data. Currently, there is a myriad of hydrologic models available that offer an array of applications. For regulatory application, accurate determination of wetland hydrology is paramount to the following: - Confirm wetland hydrologic criteria in accordance to the US Army Corps of Engineers Wetland Delineation Manual (1987 Manual) and Regional Supplements. - Establish frequency and duration (hydroperiod) of wetland ponding and flooding. - Conduct wetland functional assessments including identification of predominant water source(s). - Estimate wetland impacts from regulated activities. - Determine ecological lift in response to restoration actions (compensatory mitigation). - Establish performance standards and success criteria for compensatory mitigation. - Facilitate development of a monitoring and adaptive management plan. The objective of this report is to provide a treatise of hydrologic models that offer specific application to establish wetland hydrology for existing and future conditions in response to regulated activities and restoration actions. The emphasis is on the suitability of existing hydrologic models to hydrogeomorphic (HGM) wetland classes. HGM subclasses are not addressed in this technical note. For more details on HGM classification, see Brinson (1993).

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.