Posts tagged wetlands

Wetlands are nature’s resiliency plans, and according to the EPA the ecosystem services they provide are valued at billions of dollars. What if the 50 acre AES Redondo Beach Power Plant property currently up for sale was restored to a wetland?

Acting as natural mechanism for protection against pollution, flood and erosion, wetlands are workhorses when it comes to ecosystem services. They also provide biological diversity, fish, and wildlife habitat, while also recharging increasingly valuable groundwater. Importantly, they can also help buffer the effects of sea level rise. The City of Redondo Beach has been debating what to do with the closure of the natural gas-fired power plant for years and I believe the natural answer is to construct a wetland.

Kayakers at Los Cerritos Wetlands. Photo courtesy of Tidal Influence

Kayakers at Los Cerritos Wetlands. Photo courtesy of Tidal Influence

 

Back Bay Fens. Creative Commons photo by Andrea Monari

Back Bay Fens. Creative Commons photo by Andrea Monari

In the spirit of World Landscape Architecture Month it seems only appropriate I share a post about Frederick Law Olmstead, a towering figure in our field. To expand a bit upon Dima’s post referencing Frederick Law Olmstead’s visionary foresight, I believe he was definitely a visionary designer for his work on Boston’s Back Bay Fens. Known most famously as one of the designers of Central Park, Olmstead was also the landscape architect behind America’s first wetland restoration.

Once a tidal marsh fed by the Charles River, this Boston’s Back Bay Fens was polluted by the locals who dumped waste directly into the fragile ecosystem. At high tide, the wetland would overflow. However, at low tide “offensive exudations arose from the mud”, as Olmstead noted himself.

In the Back Bay Fens, Boston, Mass. Via Boston Public Library

In the Back Bay Fens, Boston, Mass. Via Boston Public Library

Understanding the harsh, yet ecologically sensitive and complex environment of this wetland, Olmstead knew that he had to maintain a steady water level, while also prevent refuse from entering the waterway with advanced sewer systems, and carefully selected plant material that could take the bay’s salty conditions.

Olmsted's 1887 plan for the Fens.

Olmsted’s 1887 plan for the Fens.

The first step for this wetland restoration was to dredge and reshape the wetland area so that the water traveled in a more sinuous line. Olmstead also worked with the city engineer to manage and maintain the flow from the Charles River, ensuring that the water level variation did not exceed one foot. In addition, he also coordinated a state-of-the-art sewer system to catch refuse before it entered the waterway.

Plants were planned with a long list of salt-tolerant species such as sedges, salt grass, salt cedar, sea buckhorn, and beach plum to see what would survive. Olmstead knew that the abundant plantings and cleaner water would provide habitat for water birds and aquatic wildlife.

The name Back Bay Fens was named by the landscape architect himself. Although the city commissioners were keen on calling the restored wetland, “Back Bay Park”, Olmstead knew this was no park, and referred to his old dictionary, trying out names such as “Sedgeglade” and “The Sea Glades” before settling on the final name of Back Bay Fens. Back then, the word “fen” meant “marsh” or “boggy piece of land.”

Ironically, with the damming of the Charles River years later, this once restored tidal wetland turned into a freshwater wetland. Or more specifically, a fen that receives storm water from the Charles River basin and is still more or less appropriately named to this day.

Creative Commons Photo by Jason (Audrey's Dad)

Creative Commons Photo by Jason (Audrey’s Dad)

Tanner Springs Park in Portland, Oregon is not a restored wetlands, but it mimics one. As a bold gesture of the local ecology in a post-industrial Pearl District, the park’s central feature is a stormwater management waterscape expressing the history of Tanner Creek. It’s hard to believe but Tanner Creek once flowed directly into Couch Lake, the very site now known as Pearl District.

The stormwater management method is pretty straightforward: all of the rainwater that falls on the park drains to the park’s “wetland” section and lower pond. The untreated water flows into an underground cistern, and then through an ultraviolet vault. From there the treated water is pumped up to an artificial spring, making its way down the artificial streams, and back into the “wetland.”

Creative Commons Photo by Graham Ballantyne

Creative Commons Photo by Graham Ballantyne

Creative Commons Photo by Frank Farm

Creative Commons Photo by Frank Farm

Wanting to learn more about the technical processes of this simulated wetland, I turned to the generic water treatment diagram at the park’s information kiosk, but it proved to provide little insight. I also went to the German landscape architect’s website, Atelier Dreiseitl, hoping to gain some technical insight into the functions, but again to no success.

My primary question was where Tanner Springs Park was receiving its supplemental water to sustain the park’s wetland feature between rainfall? I understand that some of the water is from stormwater, since 100% of water that lands on the site is circulated into the wetland system. But what about during days when it has not rained and water has evaporated? Yes, Portland gets a lot of rain – around 40 inches per year on average. But during the summers, it’s hot and dry. I suspected the park had another water source that sustains the park.

Creative Commons Photo by Jenny Cestnik

Creative Commons Photo by Jenny Cestnik

After searching on the internet for more information, I came across the following article from ASLA which noted:

“Rainwater will have to be occasionally topped off with city water to compensate for natural evaporation and water splash as well as Portland’s long dry summers; nevertheless, the requirement for city water will be substantially reduced. During heavy rain periods, an overflow system is tied to the city’s stormwater sewers.”

So there was my answer. I just wish there was a better diagram that communicated the whole picture of Tanner Springs Park.