Conventional vs Progressive Stormwater Management - Part Two

Fusing Environment, Art and Stormwater Management

Part Two – the Mountain Environment

In the Mountain Environment, it is important to understand that stormwater management pertains to two types of stormwater. In mountainous regions our water management issues are two fold; one, the bulk of precipitation and water supply comes in the form of snow – usually lots of it – typically between the months of October and March which is often supplemented by spring rains; and two, flashy summer afternoon monsoon driven thunderstorms that can deliver very large quantities of water and cause temporary flooding of low lying areas in a very short period of time. Winter snows will generally melt rapidly as the spring warms picking up loose sediment and road sands with the potential for seriously degrading the water quality and habitats of our lakes and waterways.  Summer thunderstorms can create broad scale damage particularly where unstabilized disturbed soils are present.

Until fairly recently the solution to this problem has been to divert stormwater to localized storm drains into pipes that release that water into local waterways and in some communities into sewage treatment plants.  More often than not that water is polluted with suspended sentiments, eroded soils, chemicals and other waste.  This results in compromised drinking water sources as well as fish and wildlife habitat.  More lately the practice of diverting stormwater to cobble lined swales and retention basins or gravel filled drywells and infiltration trenches has become very common.  This form of BMP is also referred to as ‘Gray Infrastructure.’  The good things about this practice is that it generally serves to retain stormwater on site rather than allow it run into drainage systems that deposit into sewer systems or local water bodies and also serve to help infiltrate it to help recharge groundwater.

The drawbacks lie in that there is no use of vegetation to help facilitate natural processes including evapotranspiration, nutrient and chemical uptake, and more rapid infiltration.  Additionally, this practice typically routes large concentrated volumes of stormwater through large pipes to large basins where water sits for long periods exacerbating vector and other safety related problems.  LID features are typically smaller and shallower features placed throughout an area of development, rather than at a single location, spreading stormwater more evenly resulting in potential for more efficient infiltration and reduced risk of mosquito infestation while greatly improving on aesthetics.

Please see Part Three for more...