Maximizing Biodiversity and Water With Green Rainwater Infrastructure

2021-06-25

 |  Biodiversity/Conservation

Maximizing Biodiversity and Water With Green Rainwater Infrastructure   

Amidst current changes in the climate, a combination of human influences has led to an alarming rate of global species extinction, a phenomenon that some scientists are now referring to as the sixth mass extinction. In the Pacific Northwest, the loss of biodiversity has been attributed to habitat loss, overexploitation of natural resources, habitat fragmentation and invasive species harming native species. Before urbanization, Vancouver, Canada was mostly wilderness, with many creeks and streams providing habitat for the city’s biodiversity. However, with Vancouver’s current infrastructure, the city’s biodiversity, specifically Salmon populations, are at risk. Fortunately, water management has the ability to both restore and protect this biodiversity. 

The Current Picture: climate change and the city’s infrastructure

A combination of Vancouver’s aging infrastructure, and combined sewage system has caused concern for engineers, who have identified nature-based solutions as a viable method in resolving this issue.  The city believes/research supports that implementing green rainwater infrastructure (GRI) could potentially manage both water and biodiversity within the city. In short, GRI uses plants, soils, trees and man-made structures to mimic natural hydrological processes, and  captures, cleans and returns  rainwater back into our waterways and atmosphere. With a changing climate, community values and expectations are changing alongside it – particularly around clean water bodies, increased water quality, environmental protection and healthy ecosystems within and around Vancouver.  

The city currently operates on a “combined sewage” system, in which stormwater runoff is combined in a single pipe with wastewater from homes, business and industry. During dry weather, the stormwater and wastewater are carried to the sewage plant together, and this causes no problems. However, with a changing climate and unpredictable rainfall,  the sewers can reach capacity, which would force untreated water into False Creek, the Burrard Inlet and the Fraser River (see figure 1). The problem is that as the population grows, sewage will only increase. Fortunately GRI  can alleviate pressure from the sewers, since it brings rainwater back into the water cycle while skipping the sewage system in the process. Another very crucial benefit of implementing GRI is that it will not only minimize water going into the sewage system, but will maximize biodiversity benefits altogether.

The Interconnected of Green Rainwater Infrastructure’s To Biodiversity

  1. Stream Daylighting

When , Vancouver was mostly wilderness, with many creeks and streams providing habitat for the city’s biodiversity. However, as the city grew, these creeks and streams were placed in underground culverts, making space for development. For over 50 years, Spanish Bank Creek flowed underground in a culvert and served no purpose for water management or the area’s biodiversity. When a salmon species was on the verge of extinction in the 1990s, the Vancouver Stream and Salmon Society convinced the city of Vancouver to restore the stream. The city pledged $62,000 for this work, and in 1999, 10 parking stalls and 52 meters of piping were removed, and the natural stream was recreated, including a holding pond, pools and riffles, spawning gravel, and woody debris to provide cover for fish. In addition, infiltration swales were built along the shoreline that cleaned the stormwater as it flowed off the parking lots in a process called bioretention. This process involves harmful pollutants being broken down or captured in the soils and plant roots. Once absorbed, water is taken up by plants and released as water vapor, infiltrated into the ground, or carried away by a drainage pipe into our aquatic ecosystems. This is an example of stream daylighting, a process where previously covered streams, creeks, or stormwater drains are re-exposed, which re-establishes a waterway, or creates a new channel where needed. As demonstrated in this project, daylighting streams can help restore ecological habitats, which through improved ecosystems, improve water quality (see here to learn how a healthy ecosystem improves water quality). 

Projects like this significantly improve fish migration by removing barriers and providing the habitat fish populations need to survive, all while attracting other beneficial species into the ecosystem (see here for more information). Stream daylighting also alleviates the burden of processing water, as the need to treat stormwater instead occurs naturally through bioretention.  

  1. Constructed wetlands

A constructed wetland is an artificial wetland to treat municipal or industrial wastewater, greywater, or stormwater runoff. A benefit they carry is that they are less expensive to build and operate without energy (see here for more information). Constructed wetlands can also mimic natural wetlands in  providing multiple services to wildlife. These forms of GRI consist of a basin or channel that contains water, a substrate, and plants. The elements are controlled as the wetland is created and can be designed in one of three approaches:

  • Managing wastewater – the wetland uses coal drainage systems to purify various types of waste (e.g., domestic wastewater, agricultural wastewater, stormwater runoff).
  • Control floods – the wetland increases the stormwater storage capacity and infiltration volume.
  • Habitat creation – the wetland mimics natural wetlands in providing the same ecological services for wildlife species.

New Brighton Park Salt Marsh is located in the Hastings-Sunrise district of Vancouver and was one of the city’s first port outlets. Since it was developed in the 1960s, the park had seen little change, but finally in 2017, this all changed (see here for the project). Firstly, the creation of a tidal wetland with an attached salt marsh was built. Salt marshes are one of the most productive habitats on earth and provide nutrients and organic matter that can support entire ecosystems. Afterward, the subtidal reefs were restored, which provides habitat for a plethora of marine organisms. Thirdly, Hastings Creek was restored, connecting the creek into the Burrard Inlet, opening up another entire ecosystem that would rely on the creek for habitat. By July 2017, the final construction activities were conducted on the study site, which included the planting of 25,000 salt marsh plugs, 200 native trees, and 4000 coastal shrubs. As a result of the creek being restored, riparian areas could then be restored as well. This use of GRI has given Chum and Chinook Salmon habitat, and it has been reported that these species have been seen using the salt marsh just one year after completion. As the salmon population grows, its role in the food web is restored and can serve to protect and restore biodiversity in Vancouver. 

The Connection Between Water Management and Biodiversity 

Implementing GRI is vital in providing Vancouver’s biodiversity with habitat, and the water management benefits are plentiful. Vancouver’s projects aren’t the only ones being incorporated, and GRI is growing in popularity in other cities (e.g., Seattle and Portland). Moreover, the United Nations have written extensively on the growing needs for nature based solutions, and have driven many scholars to do the same. This Vancouver case study is just one small contribution, led by many scholars around the world making positive discoveries in their research on the benefits of nature based solutions in urban contexts. 

In a changing climate, managing the city’s water while protecting biodiversity is not only a hope, but an expectation. In addition to current projects, City of Vancouver staff are finding new ways in which GRI can benefit both the people and the environment. Seeing municipalities working toward solving these issues is exciting, and will hopefully continue at a great pace. 

Glossary: 

Biodiversity: Biological variety and variability of life on earth. Biodiversity is a measure of variation at the genetic, species and ecosystem level. 

Bioretention: a type of green rainwater infrastructure that captures and cleans urban rainwater runoff. It typically consists of a shallow depression or basin that features layers of rock, engineered soils, and resilient vegetation that can tolerate periods of inundation and drought. 

Combined Sewage System: a type of sewer system in which one set of pipes carries both sanitary sewage and urban rainwater runoff. (For technical definition, see the Sewer and Watercourse By-law). 

Constructed Wetland: An artificial wetland to treat wastewater, greywater or stormwater runoff. Also designed to restore damaged wildlife habitat. 

Green Rainwater Infrastructure: a suite of rainwater management tools that use both engineered and nature based solutions to protect, restore, and mimic the natural water cycle. 

Infiltration Swales: Vegetated open channels specifically designed to attenuate and treat stormwater runoff for a defined water volume. 

Nature Based Solutions: design solutions that are inspired and supported by nature, which are cost-effective and simultaneously provide environmental, social, economic benefits and help build resilience.

Riparian Areas: Riparian areas are defined as the vegetation growing along the edge of a water body. 

Salt Marsh: An area of coastal grassland that is regularly flooded by seawater. 

Stream Daylighting: Opening up buried watercourses and restoring them to more natural conditions. 

Subtidal Reef: Subtidal marine ecosystem dominated by ridge-like or mount-like structures formed by the colonization and growth of marine organisms. 

Wastewater Facility: Wastewater treatment is the process used to remove contaminants from wastewater or sewage and convert it into an effluent that can be returned to the water cycle with acceptable impact on the environment, or reused for various purposes. 

Water Utility Services: Services that provide drinking and wastewater services to residential, commercial, and industrial sectors of the economy – typically public utilities operate water supply networks.