If I had to name the single greatest factor for flooding or flood related problems on properties not in flood zones, it would be the lack of maintenance to the drainage system.  By drainage system, I mean swales, ditches, storm drain inlets, downspouts, gutters, and any surface or concentration point that collects or moves rain water.  Here are what I think are some of the key points to maintaining a clean drainage system, and preventing flooding on your property.

• Each fall, before the rainy season begins, clean out your gutters, run water (via a hose) down your roof drain downspouts to check for leaks and that water is exiting freely, and clear out any debris from drain grates, as well as within the drainage inlets and storm drain pipes.  Water test your storm drain pipes (if you have them on your property), and make sure they actually work.  Have a local sewer service company come and clean out your pipes if you can’t do it yourself.
• Repeat the above for each spring, after the rainy season, if you had any flooding during the winter.
• During the rainy season, a day before expected rain, check out your drain inlets on your property, and clear out trash and debris.  Are your inlets filled with silt or landscape debris (branches, mulch, leaves)?  Shovel them out.  If you do this quick check before each storm, it won’t take much time.  But, if you wait ’till there’s a problem, then it can be costly.

Marin County’s Stormwater Program is undergoing changes that will affect all developments that create or replace as little as 2,500 square feet of impervious surfaces, including detached single family residences that are not part of a larger development.  Unless edits occur to the final order now on file with the State Water Resources Control Board, this change will commence July 1, 2013.  In addition, starting July 1, 2014, projects that create or replace 5,000 square feet of impervious surfaces (not including single family residences that are not part of a larger development) will require implementation of site design, source control, runoff reduction, storm water treatment and baseline hydromodification management.

What affect might this have on you or your project?  Give us a call, and we’d be happy to assist you.  Call 707-792-1800, and ask for Michael Tarnoff, vice president of engineering, and certified QSP/QSD with the California Stormwater Quality Association.  Or, email Michael at michael@firmadesigngroup.com

Global warming notwithstanding, we have quietly entered the “rainy” season for the Bay Area.  Is your site buttoned up for light storms, long storms, or heavy intense storms?  Which erosion control measures are you using?  Are they the most cost effective for your site?

Some erosion control basics:  Straw wattles (aka fiber rolls) are only effective if installed properly; they need to be placed on contour, and not sloped;  the need to be held down to the grond tightly; and by using biodegradable mesh, you protect the environment from plastic, and save on disposal costs.  Gravel bags are great at protecting inlets; they should be packed loose enough to allow water to penetrate through, but hold back sediment; tightly packged bags, or sand filled bags will simply create a dam condition that may not function as a sediment block.  Straw mulch protects barren slopes and areas.  Better still, hydroseeding provides an inexpensive way to stabilize a slope without constant maintenance.  Silt fences are best used as a last line of defense, and should be preceeded by other erosion control measures.

As your choice for creative landscape architecture and civil engineering solutions, Firma Design Group can quickly step in and provide erosion and sediment control assistance.  Call us today at 707-792-1800, or email us at office@firmadesigngroup.com.

Passing along this cool article in Geosynthetics magazine about the installation of geomembrane curtains at the Whiskeytown Reservoir in order to lower water temperatures (needed for successful salmon spawning – in this case, chinook salmon).  Check it out!

http://geosyntheticsmagazine.com/articles/0612_f1_geomembrane_curtain.html