Big Canyon is the largest remaining natural canyon on the east side of Newport Bay.  It has been informally designated as a Nature Park, but it has been heavily influenced by the construction of a salt evaporation pond, historical placement of dredge and fill material, interim restoration efforts, and other human activities.  Stockpiling of dredge fill during the 1950s and 1960s within Big Canyon Creek raised the elevations within the canyon and consequently channelized the creek to the north.  The creek now winds through the Nature Park in a general southeast to northwest direction and then discharges into Upper Newport Bay.

Big Canyon - photo 1

Figure 1: Plans for Big Canyon Restoration.  Black outline, phase I; Yellow outline, phase 2A; Red outline, phase 2B; Blue outline, phase 2C.  Pink dots are the Brazilian pepper trees.  About 50 pepper trees are also present but not shown in the area outlined in blue.

The upper 45-acre parcel of Big Canyon Nature Park (Outlined in black and yellow in Figure 1) is owned by the City of Newport Beach, while the lower 15-acre portion is owned the California Department of Fish and Wildlife (CDFW) and is a part of the Upper Newport Bay State Ecological Reserve.

Big Canyon has some small fragments of Southern Riparian Forest dominated by Alkali heath (Frankenia salina) and Coastal Sage Scrub native plant communities.  Unfortunately, these communities are fragmented, disconnected, and being overwhelmed by invasive species, especially the hyper-invasive Brazilian pepper tree (Schinus terebinthifolius; Figure 2).  Proliferation of these pepper trees has led to the formation 0f a 4.3–acre forest, containing little vegetation other than pepper trees, in Big Canyon (Figure 1 and 3a,b).  Production of “allelopathic” chemicals by the trees prevents germination and growth of most plants underneath them, leading to a dramatic reduction of plant biodiversity as well as loss of cover for native animals.  Similar problems with these invasive trees has led to even bigger environmental impacts in Texas and Florida, even in Everglades National Park.

Big Canyon - brazilian pepper

Figure 2. Brazilian Pepper Tree, Schinus terebinthifolius

In Phase 2A, the Newport Bay Conservancy will work in collaboration with the City of Newport Beach and the California Department of Fish and Wildlife (CDFW) (property owners) to arrange to remove part of the peppertree forest and replace it with native riparian vegetation.  This phase also includes a Feasibility Study to replace the remainder of the peppertree forest and (Phase 2B) to develop the least impactful and most cost-effective approach to restoring or removing the freshwater pond in the lower portion of Big Canyon (In the area outlined in red).  The pond is the largest mosquito breeding habitat area in Orange County, and sediments and aquatic vegetation in the pond are contaminated with selenium originating from the upper portion of the watershed.  Phase 2C will be the planning phase for restoration of the low-lying area of CDFW property (outlined in blue).Several plans have been drawn up for the restoration of Big Canyon, but none has previously been implemented. In the current Restoration Project, Phase 1 (outlined in black in Figure 2 and shown in detail in Figure 3) has been funded and is being managed by the City of Newport Beach in the upper part of the canyon.  It includes creek and riparian habitat restoration, the construction of a stormwater treatment bioretention cell and wetlands, as well as dry-weather flow diversions, culvert improvements, and trail planning.

Big Canyon - site photos

 Figure 3: Different parts of Big Canyon. a, Forested area shown in yellow in Figure 2; b, Forest of Brazilian peppertrees in the interior of area shown in yellow in Figure 2; c, “Freshwater pond” invaded by cattails, in area outlined in red in Figure 2; d, Area shown in blue (foreground) and red (background) in Figure 2.

Big Canyon - last map

Figure 4: Plans for the bioretention basin and associated infrastructure for phase 1 of the Big Canyon Restoration Project.

For more information on Big Canyon, visit the City of Newport Beach’s Resource and Recreation Management Plan for the entire space.

Written by Peter Bryant

President, Newport Bay Conservancy

Reference: Pohl, D. H. (2016). Coastal Creek Restoration and Estuary Adaption Project in the Big Canyon Nature Park – Phase II. Grant Application to California Coastal Conservancy from Environmental Science Associates, San Diego, CA.