Lightning storms and heavy rains wreaked havoc on Southern California earlier today.
Today seemed more odd being in Los Angeles than usual because this has been the Summer of hot hot hot nonstop. Did I mention how hot it has been? I normally decide to wash my car, end up having to go to a rush meeting and then it rains just enough to make it all for not. I feel like I can start to tell the future as I chose not to wash the car this week as I knew there would be a few out of nowhere meetings. Do these meetings coincide with the weather? I could write a formula that might back up my feelings being fact. But math is sometimes boring and the flash floods had me more glued to the news than normal. So what did I learn today instead of some made up equation?
I learned that the most recent storms that hit Southern California are good examples of why Civil Engineers do what they do. Watching the news and seeing the flooding really puts drainage plans into perspective. How do these go together? We must design our drainage or grading plans to drain the water off of a property to go somewhere. That somewhere is generally into the street fronting the property. From there the water normally collects into a gutter which goes into a storm drain catch basin. Next the water travels from the storm drain to the ocean, nice and unfiltered. Yes most people don’t know that the little do not put garbage into the storm drain really does mean this goes straight to the ocean. The sewer and storm drain are two different things.
Now what does the storm drain and storm water have to do with anything? Everything! We consistently have clients asking why we are sizing drainage devices to be so large even though it barely ever rains in Los Angeles or Southern California. The answer is that the type of rain Southern California gets is actually pretty intense. I won’t go into what we do exactly. But we use Hydrology manuals and a calculator or Excel spreadsheet which determines the amount of storm water that will occur on a particular site based on some given criteria. The main criteria lately has been do we design for the 25 or 50 year storm. Most cities accept designing for a 25 year storm as a minimum. So we do this when it makes sense. Though we like to design for a 50 year storm as a safety factor.
This latest storms reminds me that I need to show videos of these storms to explain how important proper drainage design is on a site. This has more to do with pipe sizing as most storm water must now be guided into drainage devices that will filter the water and when possible send the majority of that storm water into infiltration pits. And then any overflow will go into the public storm drain system. So next time it rains, take a look at the infrastructure surrounding you as there is a lot more going on with your everyday environment.