What do you know about stormwater? The science of determining how much runoff will be generated from a storm event is complex. Given a set of criteria such as land use, contaminants, slope, soil type, previous rainfall (antecedent moisture content), impervious areas, (roofs, roads, and driveways), snowpack, and temperature how does a stormwater engineer determine which ones are critical?
For the average project, it may be reasonable to make assumptions about many of these variables, but sometimes it is important to determine and model the processes that are occurring. Knowing when to ramp up the design effort requires some experience, but can usually be guided by simple engineering risk management principles and a review of the legislation that the project may fall under. Sometimes the effort in design and project management can offset huge consequences.
Just this week there have been reports out of the US of several projects where appropriate risk management may not have occurred. All of these examples are from the website stormwaterauthority.org, a good source of stormwater news and documentation of Best Management Practices used in the States.
Motoring along Interstate 5 in Lewis County near Winlock at exit 63, drivers can see the latest landowner illegally clearing land without a permit, causing sediment-laden water to run into a salmon bearing waterway. The Washington Department of Ecology has stepped up its actions against a landowner responsible for sending muddy water into Lacamas Creek while clearing a 190 acre site mainly consisting of wetlands.
The Avondale Water and Sanitation District in Pueblo County, Colorado is in big trouble with the U.S. Environmental Protection Agency for illegally rerouting a river. The federal agency has ordered the Avondale district to restore the segment of the Arkansas River it re-engineered.
The violations occurred… in Anchorage, Alaska. The stormwater discharges from the site entered Campbell Creek, a tributary of Campbell Lake where salmon are still found. Both Campbell Creek and Campbell Lake are “navigable waters” under the law and are waters of the United States.
These three examples highlight the risk of any project near or potentially impacting a waterway, and that even government organizations such as water and sanitation districts are not immune to federal legislation requirements. The legislation may be different around the world, but the need to ensure full compliance with local laws and best practice remains regardless. As developers, engineers or government agencies the first step is understanding your obligation under the local laws, then implementing risk management analysis to determine what measures or design features should be implemented to ensure compliance with these laws.
In each of these cases above, the same action fifty years ago may not have raised an eyebrow, but with our improved understanding of habitats and watershed management, the rules are tougher, and more expensive to mitigate against. Rivers, creeks, lakes and wetlands (previously called swamps) have amazingly diverse functions such as aquatic and wildlife habitat, potable water supply, flood attenuation, groundwater recharge, as well as recreation and aesthetic uses. In Newcaslte, Australia, the city we moved from a year ago, the local government had a program in place to rate the quality of aquatic wildlife in many of the urban creeks. This is called Creeks Alive, and is an opportunity for the community to be involved in protecting and rehabilitating the creeks that surround their homes. Also a year ago, (almost!), I wrote an article about frogs – which I dubbed our eco-canaries, these are the indicators of our stream health, when they start disappearing, it’s time to wonder what you are doing wrong.