Seven Days in December - San Elijo Lagoon Conservancy

Storms continued from Page 1
What does this kind of rain event mean for San Elijo Lagoon and
other coastal wetlands? Periodic flooding is a normal part of life
in riparian zones like Escondido Creek. It’s typically a restorative
event—sediments, nutrients and organic matter carried by storm
flows are moved out of the channel and deposited on the floodplain,
nourishing riparian plants and creating mixed habitat and protective
cover for aquatic organisms. For an estuary like San Elijo Lagoon,
these same flows would normally move excess sediments and
nutrients out of the lagoon and into the ocean, providing new sand
for North County beaches.
Unfortunately, in an urban watershed, these “normal” hydrological
processes are often compromised by the impacts of increased
population and development. Extensive impervious cover in the
watershed (streets, driveways, parking lots, etc.) increases the flood
magnitude and the water velocity over a very short period of time as
this water is delivered almost immediately to storm drains and their
receiving waters. Channel bottoms are quickly scoured and banks can
collapse, increasing the sediment loads downstream. These two factors
alone (flood magnitude and velocity) can overwhelm a watershed’s
natural tendency to slow the flood’s flow over the floodplain.
FUN FISH FACTS
the lagoon. Some of the common species include Killifish,
Clevelandia ios
Striped mullet
Mugil cephalus
9.0
8.0
Stream Level on Escondido Creek at Camino del Norte Bridge
Mosquitofish, Carp, Catfish, Green Sunfish, and Blue Gill are
7.0
Stream Level (feet)
6.0
5.0
4.0
3.0
Mosquitofish
Gambusia affinis
2.0
1.0
0.0
12/1 12/16 12/18 12/20 12/22 12/24 12/26 12/28 12/30
Date in 2010
Note how quickly the stream levels rise. This is typical of streams
surrounded by urban development and impervious cover.
Impacts to wetlands in arid Southern California are magnified when a
flood event hits harder and faster than it would in the absence of urban
influences. This is why the Conservancy is working with its neighbors
and local cities to make sure that future development in the watershed
employs Low Impact Development (LID) concepts and “buffer zones”
around riparian areas. Remaining mindful of how water moves in a
watershed, and the human activities that change it, is increasingly
important as our coastal population continues to grow.
Find us at www.facebook.com/sanelijo.
NEW INVASIVE PLANT FOUND IN THE RESERVE!
Dittrichia
graveolens
on the Gemma Parks loop (Rios Trail). It is an annual herb that
to cling to clothing, tires, and equipment. Plant oils may cause
contact dermatitis, headaches, blistering, and itchiness. It
produces copious amounts
of seed (~15,000 seeds per
once established. Although the
removed, it is highly likely that
more are present. Please alert us
(plants@SanElijo.org) if you see
it. Do not attempt to remove it.
Rapid response and treatment
keep it out of our yards and
natural areas.
Photo: R. Preston, Calphotos, Berkeley
6 | Lagoon Tidings Winter 2011