Chapters 1 - U.S. Fish and Wildlife Service

Chapter 4
With the exception of the area restored by the Port of Long Beach in 1990, the configuration of the
marsh plain and associated tidal channels protected within the Refuge boundary remains much the
same as it was in the 1800s (refer to Figure 4-5). Although wider in some places and more
constricted in others, the tidal creeks remain in essentially the same locations, as does the
extensive marsh plain. Habitat quality has however been compromised to some degree by a
reduction in the marsh’s tidal prism following the completion of Huntington Harbour, as well as by
the significant reduction in seasonal freshwater flows that once flowed into the marsh. The volume
of freshwater entering the marsh was significantly reduced following the flood of 1862, which
changed the course of the Santa Ana River, diverting the floodway well to the south of Anaheim
Bay. As a result of this and other major flood events, the watershed upstream of Anaheim Bay
continued to be altered through the construction of flood control channels, including the
construction of the Bolsa Chica and East Garden Grove-Wintersburg flood control channels.
These channels divert essentially all of the freshwater flow from the streams and creeks upstream
of Anaheim Bay. Instead of following through the marsh, these flows follow a man-made channel
around the eastern edge of NWSSB and empty directly into the western end of Anaheim Bay
(Figure 4-6). Despite the changes that have occurred in Anaheim Bay over the past 100 years, 748
acres of the marsh remain essentially intact and represent some of the best quality coastal wetland
habitat remaining in southern California. This is due in large part to regular, unobstructed tidal
influence that supports a diversity of plants, fish, birds, and other coastal dependent organisms.
4.2 Physical Environment
Elements of the physical environment include topography, visual quality, geology/soils,
agricultural resources, mineral resources, paleontology, hydrology/water quality, climate/climate
change/sea level rise, air quality, greenhouse gas emissions, contaminants, and noise.
The Quaternary alluvium floodplains that dominant the area included within the Seal Beach NWR
were formed during recent times, therefore the potential for the presence of paleontological
resources beneath the surface is very low, particularly in the upper levels of the formation. Fossils
have however been found at greater depths in nearby areas underlain by the same geological
formations. Because of the low potential for paleontological resources and the limited potential for
significant ground disturbing activity on the Refuge, no effects to paleontological resources are
anticipated; therefore, this topic is not addressed any further in the EA. Similarly, the Seal Beach
NWR is not located in proximity to any sensitive noise receptors (e.g., housing, hospitals, libraries),
therefore, there is no potential for adverse noise impacts to such uses as a result of activitities
occurring on the Refuge. No further discussion related to noise is therefore required.
4.2.1 Topography/Visual Quality
The elevations within the 965-acre Refuge range from -2.0 feet below mean sea level (MSL) to just
over 9.0 feet above MSL. The majority of the Refuge, approximately 793 acres, supports tidal
channels, associated mud flats, and extensive areas of salt marsh (Figure 4-7). The areas restored
as part of the Port of Long Beach mitigation project include 116 acres divided among four tidal
basins and several feeder channels that facilitate tidal exchange within the basins. Forrestal and
Perimeter ponds support open water habitat, while Case Road Pond and 7 th Street Pond support a
combination of open water, salt marsh, and periodically exposed mudflats. The Case Road and 7 th
Street Ponds also include constructed islands that support a range of intertidal habitats. These
islands average about 1.7 feet above MSL. The easternmost island in the Case Road Pond includes
several mounds that achieve an elevation of approximately four feet above MSL.
4-8 Seal Beach National Wildlife Refuge