This weekend I volunteered to warn shopkeepers and
officials in my San Francisco suburb about dangerous urban flooding potential during
the next week.
Every Friday noon in San Anselmo the “flood siren”
(not disaster siren, mind) is tested. Within fifteen minutes of the last time
it blasted for real in 2005, at 3:30 a.m. on a Saturday, three to four
feet of water was soon gushing down the main street (see photo above) into
homes and businesses. People here are acutely sensitive to heavy rain and the level
of the town’s creek, since they are still trying to rise up from that cold watery blow
four years ago.
Up and down the California coast, metro areas
including Los Angeles and San Francisco, are experiencing a series of El
Nino-generated Pacific storms. Further inland, Phoenix will also take a big
hit. The forecasted 6-10 inches of rain over the next days will almost
certainly bring localized flooding and mudslides. Ocean storm swells will reach
20-30 feet on some parts of the coast by Thursday, lashing roads,
infrastructure and housing. (Update Jan. 22: the storms this week luckily did not flood San Anselmo, but did cause heavy rains, some flooding and infrastructure damage throughout the state and Arizona, while also reducing the region’s drought).
NOAA 5-day precipitation forecast from 1/16/10: small purple circles in California represent areas expected to receive 8+ inches.
How much of this weather and its impacts can be
directly attributed to global climate change, I will not venture. The coastal
and tidal flooding that is expected in California, however, will be one of the hallmarks of a changing climate. Another effect will be drought—which
California and the Southwest have been experiencing for three years–the flip
side of climate change’s growing precipitation impacts. Coastal
and desert urban areas in particular need to steel themselves for such a schizophrenic
Leaving things up to “officials” to figure out disaster
plans is not recommended; true community resilience will require research, networking
and knowledge sharing within and outside one’s normal sphere. In my case, I think
I was able to plug a few vital holes that may have been missed.
Most store owners in San
Anselmo (pop. 12,000) that I spoke with were savvy about imminent flood danger.
Based on their experience with the New Year’s Eve flood of 2005, a few
shopkeepers had excellent information and resources: they referred me to online
creek-level readings (“anything over ten feet and I’m out of here,” one man said), and email alerts that can be sent to email or phones from Nixle.com, a national information mass customization service that localizes updates on disasters, road
closures and crime.
Nixle, for instance, has newly
updated postings from the San Anselmo Police Department about potential hazards
for flooding and safeguards.
There’s even a local AM radio (1610) station dedicated to disaster updates for
But none of that seemed to be
enough to really prepare people. One friend, a council member from the
neighboring town that was also flooded in 2005, did not know about the severity
of the forecast weather when I chanced to run into him at a musical performance
over the weekend. He had me send him the forecast links from NOAA
showing him exactly how much precip is expected to fall.
He emailed back, “We’re trying to get our flood plain residents to batten down
the hatches. This should help.”
Other small business owners
that I spoke to were new to town, including immigrants. Unlike long-time
business owners who told me they were warned by the police (or that had vivid mud-damaged
inventory and moldy wallboard memories), the new shopkeepers knew almost nothing
about flooding dangers or where to get the free sandbags.
Those who were around in
December 30, 2005, have learned that floodgates (above, white board) for each business offers the
best protection. In actuality, these are just rails installed on each side of entrance
door where a piece of plywood can be inserted as a barrier against the torrents
of water can come crashing against and under the front shop door (usually
glass). Gates work even better than sandbags, but sandbags will prevent the
glass doors from being smashed open.
The town and surrounding
communities, even the federal government, tried to take some larger-scale policy
actions after the 2005 flood, which caused almost $100 million in property damages
county-wide. The Federal Emergency Management Agency (FEMA) developed a new local flood
risk map based on the 2005 event, and insurers offered policies that residents within
the areas were urged to purchase.
An extensive engineering study of the region’s watershed is being made,
a $125-per-property flood fee narrowly passed a controversial vote, while creek debris clean-ups have become popular all-age volunteer events each fall before
the winter rainy season arrives.
Some houses have been rebuilt
and raised above the flood-prone region along San Anselmo/Corte Madera Creek. This
normally placid creek empties seven miles later into San Francisco Bay. High bay
tides back the creek up so that it can’t empty into the bay quickly.
San Anselmo/ Corte Madera Creek Watershed: San Anselmo is in center, San Francisco Bay, on right
Unfortunately, it doesn’t
take much time for San Anselmo/Corte Madera Creek (watershed in brown above) to back up from San Francisco
Bay and rise in the Marin communities lining its flood plain, since it is
surrounded by steep canyons that channel rainfall off nearby hills. Asphalt
parking lots, impermeable pavement and poorly planned development have also
increased the speed by which rainwater runs off into the creek. For instance,
when I checked creek levels online Sunday the 17th, the creek was 2.9 feet, but after heavy rains Sunday night
and Monday morning the creek was already over 6 feet. Flood stage is 11 feet (update 1/20/10: after heavy rain, the creek level went from 4 feet to 10 feet in matter of five hours, before receeding slightly) .
The irony of California’s
winter storms is that they bring needed water to reservoirs and mountain snowpack,
promising to reduce or temporarily end the region’s ongoing drought, which has
been costing the agriculture industry and some cities hundreds of millions in
lost revenue and in water purchases. Marin County last year was the first in
the Bay Area to approve desalination from San Francisco Bay water, despite energy and marine environmental impacts along with a hefty $100
million-plus price tag.
Not surprisingly, the state’s residents have a
love-hate relationship with their winter weather. To make the affair even more
volatile, climate change may be swinging the status from drought to flood in a
matter of a few weeks.
Indeed, California’s coastal
metros (along with the Gulf Coast, including Florida and New Orleans) may be
the first litmus test for how to adapt to the unpredictable excesses and
scarcities of a changing climate.
active urban sustainability strategy consultancy. He is author of How Green is Your City? The
SustainLane US City Rankings and a Fellow at the Post Carbon Institute.