In our most recent article we focused on the threats to marshlands, and the ecosystem services they provide, from sea level rise. Now, we’re going to focus on the hidden threats from sea level rise.
Remember back to those good old days when the sea just rose and fell with the tides? Now and then there would be a big storm but it would pass and everything would go back to normal. Well, climate change is making those storms bigger and wetter, and it is already causing sea level rise.
You would think that we can just build levees and seawalls and that would keep the sea out of our lands. But, it isn’t so easy. Below the surface of the land are vast reservoirs of groundwater. Groundwater is rain water that has soaked into the ground over many, many years.
Seawater also seeps into the ground under the sea floor. Seawater is salty and is heavier than groundwater. At the shoreline where the two waters collide under the surface of the land, the seawater stays under the groundwater. So when the sea rises, not only does the water flood across the beaches, mud flats, wetlands, and our communities, but under the surface, the seawater also pushes up the groundwater, contributing to more surface flooding and wreaking havoc underground where we can’t see it.
So, in spite of the levees which we build, to protect us from sea level rise, the seawater can move under the levees, pushing up the groundwater, causing a number of problems on what we thought was dry land. Our creeks and low lying lands can be flooded as well as our grey infrastructure, our roads, parking lots, and basements of buildings. Water soaked electrical systems could fail. Water seeping into cracked sewer pipes can drown out waste water systems, which weren’t designed to carry that kind of load, and this can cause an overflow of untreated water into the environment.
There are hundreds of contaminated industrial sites, land fills, and old dumps, on the shores of San Francisco Bay, where the clean up or containment strategies may not stand up to the new threat of groundwater rise. Many of these old toxic dumps were covered with a cement or clay surface, and simply left in place. Some have even been built upon. It was thought that if the cap was well built, this was a safe practice, but groundwater rise challenges that assumption.
When groundwater flows under the surface caps of the old dumps, the toxins which were inert when capped in dry soil, can move and spread as the groundwater moves and spreads in the soil. These toxins, many of which are known poisons like mercury, chromium, oil and gas products, lead, etc., can end up in our streets, in our backyards, in our basements, and in our Bay sickening our people and the animals and plants that support our healthy ecology.
That would be catastrophic.
And unfairly, most of these sites are in communities that have the fewest resources to deal with this problem. Getting involved and taking action is easier than you think. We know the seas are rising, and the time to join together is now to help all communities assess and start cleaning up toxic sites.
Join the Sierra Club’s Bay Alive Campaign to help protect our Bay from these effects of groundwater rise.