- they shade the water and keep it cooler compared to when it runs off a parking lot;
- it slows the flow of the water down and allowing sediment to settle out;
- plants assist in the settling and breakdown of pollutants and contaminants in the runoff;
- plant roots open up the soil thus allowing for more infiltration and recharge of the groundwater;
- plants bring oxygen into the soil which greatly enhances the breakdown of contaminants in the water;
- wetland areas are among the most productive ecosystems in the world and are great in removing air pollutants and CO2 out of the air; and finally,
- all these plants provide great habitat for all kinds of critters such as insects, amphibians, reptiles, birds and even mammals.
Thursday, June 25, 2015
I’ll be mixing work and pleasure in today’s blog entry.
The more southern part of York County or lower York County (we divide county into the lower and upper part, with the division being the Yorktown Naval Weapon Station) is very flat, and we experience a lot of flooding during heavy rainstorm events. Flooding was so bad that the county started a Stormwater Advisory Committee (a citizens group), of which I was a long-term member. We advised the county on where to invest in projects that improved the stormwater infrastructure. We also served as a conduit between citizens and the county and developed a set of publications that citizens could use in managing stormwater in and around their homes and in their subdivisions. Regretfully, the County Commissioners decided to disband the committee a few years ago, and I will not go into why they did that.
Fast forward to this week. The county has been building this huge bioretention area near one of our high schools. Bioretention areas are what they are called. They store and retain stormwater in an area for some time to allow it to infiltrate into the soil. Excess water is slowly released into a drainage way, creek, or stream. The word bio stands for that there is some biology involved with all of this, and in stormwater that means plants. The photo below shows the area just after it is planted.
Regular readers of my blog know that I teach all things stormwater in my current job. Lately I have been teaching about plants that can be used in exactly these kinds of projects and I was encouraged to see what plant species they used in their planting. Why plants? Well, plants have all kinds of benefits:
Another wonderful thing to see is that the bottom of the area is not flat and uniform. You can see islands which will be flooded temporarily during a storm and some permanent pools (the darker areas). This greatly enhances the diversity of the area and all those functions I talked about above.
Why is this so important that I run around the state to teach it? Well, in the old days when there were less people and less impervious areas such as roads, roofs, parking lots, sidewalks and driveways in our country, rainwater was able to infiltrate into the soil and recharge the groundwater table. Nowadays, we are pumping the groundwater faster than rainfall can recharge it. In addition all that rainwater runs off as stormwater and because it did not infiltrate the amount of water that runs off has greatly increased. Streams cannot handle all this water and we see increased flooding, erosion in streams and increase damage to the stream banks. All these bioretention areas and stormwater ponds are designed to lower the impact of development, decrease flooding as much as possible, clean up water and recharge the groundwater.