West Depression

West Depression Monitoring Report

West Depression is a 1 acre coastal dune habitat area between Manzanita Village restoration site and Lagoon Island. The primary outfall from the Campus Lagoon is from a weir that conveys water underneath West Depression into an outfall box on the beach.

Figure 1: Location of West Depression

In 2005 the site was relatively flat with very little topographic variation and completely dominated by iceplant (Carpobrotus edulis) with native dune and salt marsh plants along the more extreme margins and intermittent patches of non-native ripgut brome (Bromus diandrus) throughout the site. Iceplant was controlled by method of 'solarization' using sheets of black plastic (6 mm thick) to trap heat and moisture and block sunlight from August - December, 2005. Native species were seeded and planted during the winter and spring of 2006 into three habitat zones created as part of the project: coastal dunes, coastal sage scrub, dune swale, coastal strand, and salt marsh. Extensive hand-weeding of ripgut brome grass (Bromus diandrus) was required during the spring and summer of 2006 in order to decrease competition to native plant establishment and keep the non-native grasses from setting seed. Species diversity on the site has increased from an iceplant monoculture to a diverse native-dominated plant community with over 35 native species.


Figure 2: West Depression in 2004, covered in iceplant.

Figure 3: Black plastic traps in heat and blocks sunlight, causing the iceplant to die.


Significant natural events have affected the site and reflect a regime of disturbance characteristic of coastal dune sites. Namely, high tides and large wave events coincided on December 21st, 2005 and in January 2008. These events brought in huge quantities of seaweed and wracks of driftwood and Arundo donax along with pulses of sea water. The first event occurred when the black plastic was still covering the ground, so in the process of using heavy equipment to unearth the plastic some topography was created to form a shallow swale which favors salt marsh vegetation and some small foredunes which support a variety of dune species. The 2008 event brought a seawater and driftwood pulse which partially leveled the foredunes and altered the soil salinity so that several coastal sage scrub species, such as Artemisia californica and Encelia californica, died. The result is that the ocean side of the project has been re-set to an early successional stage in dune formation dominated by beach salt bush (Atriplex leucophylla) and beach bur (Ambrosia chamissonis). Interestingly, historically such intense storm events are not common; in fact the 2005 event was the first time in 25 years that high tides and waves from a storm had breached the lagoon. It is unusual that these two storm events occurred so close together.


Figure 4: Large waves in 2005 flooded the site and covered the site with seaweed and driftwood.

Figure 5: Driftwood and seaweed after a large storm.



Figure 6: Heavy machinery had to be used to remove buried black plastic use for ice plant solarizaiton.


Native Species at West Depression

Latin Name Common Name
Abronia maritima Red sand verbena
Abronia umbellata Pink sand verbena
Ambrosia chamissonis Beach bur
Ambrosia psilostachya Western ragweed
Artemisia californica Coastal sagebush
Atriplex californica California saltbush
Atriplex leucophylla Beach saltbush
Atriplex triangularis Spearscale
Baccharis pilularis Coyote brush
Calystegia macrostegia Morning glory
Cuscuta salina Dodder (parasitic plant)
Camissonia cheiranthifolia Beach evening primrose
Distichlis spicata Saltgrass
Encelia californica Bush sunflower
Eriogonum parviflorum Seacliff buckwheat
Eriophyllum confertiflorum Golden yarrow
Eschscholzia californica California poppy
Euthamia occidentalis California goldenrod
Frankenia salina Alkali heath
Gnaphalium californicum California everlasting
Grindelia camporum Gum plant
Heliotropium curassavicum Beach heliotrope
Isocoma menziesii Coast goldenbush
Jaumea carnosa Marsh jaumea
Juncus acutus Spiny rush
Juncus mexicanus Mexican rush
Juncus patens Common rush
Limonium californicum Sea Lavender
Lotus scoparius ssp. scoparius Deerweed
Lupinus arboreus Bush lupine
Malacothrix saxatilis Seacliff daisy
Malvella leprosa Alkali mallow
Mimulus aurantiacus Bush monkeyflower
Mononthochloe littoralis Shoregrass
Phacelia ramossisima Branching phacelia
Solanum douglasii Douglas' nightshade
Spergularia macrotheca Sticky sandspurry
Spergularia marina Salt sandspurry
Verbena lasiostachys Western verbena