With a flair for the pun, I chose this topic today because I know that to those who have something to do with stormwater but who don’t make their living designing it, writing about it, thinking about it everyday, the changing research, requirements, and regulations in the stormwater world must be perplexing. Its all, though, really quite simple.
Stormwater is a complex topic. Nominally, rain falls, it flows away, and its gone. That’s the most simplistic way to see it and its how the world of engineering saw it for a very long time. Things have changed. Behind the simple approach is the real interest. As rain falls, it has certain effects on the natural and built environment. These effects, and the effects the natural and built environment have on the rainwater, define the areas where, in my opinion, stormwater becomes interesting. For instance, did you know that we used to model storms based on them coming and going in a general patterns depending on geography? Did you know that various organizations have ‘typed’ storms based on those patterns? Did you know that the pollutant load from a particular storm varies significantly depending on the time of year?
Although it has rained in the Pacific Northwest and everywhere else on the earth for millenia, we have only really endeavored to understand rain within the last 100 or so years. We have kept rainfall records and used those records to create mathematical models to understand the runoff a particular storm will generate and the effect that runoff will have on man-made conveyances, lakes, rivers, and, ultimately, the receiving oceans. Those models have been reviewed, revised, sometimes dispensed with and other times perfected. Its not the rain that has changed, but the accuracy of our mathematical models have improved, causing us to change the stormwater runoff calculations and, therefore, the regulations.
These changes have had a great effect on what gets built. Forty or more years ago, stormwater collection and conveyance was only a minimal part of a civil engineer’s design. Thirty years ago, our early design methodologies resulted in small ponds and water quality features. Twenty years ago, we began changing the calculations and requiring larger stormwater facilities. Ten to fifteen years ago, we had another change in how much we understood. It has been a great 30-40 years where we really improved our knowledge of stormwater. As a result, runoff is cleaner.
Where to from here? It seems that we have done some great work in modeling how stormwater flows, in calculating the volumes of storms, and in determining methodologies to design stormwater facilities. Next, in my opinion, is getting a better handle on keeping those systems operating and maintained. That is the challenge for the next forty years.