Historically, many of the largest cities and towns in the world are built along rivers because they promote industry, recreation, and food production. Despite whole communities thriving off of these bodies of water, their health and longevity is constantly being threatened by man-made factors such as pollution, streambank development, and increased erosion and flowrate. If we are to take action to preserve the futures of our rivers and streams we must first gain a strong understanding of these threats and how increasing riparian vegetation has the potential to address them.
All forms of pollution fall into one of two categories: point-source and nonpoint-source pollution. Point-source pollution cane easily be traced back to a single source such as a power plant, factory, or water treatment plant. The pollutants from these buildings end up in waterways via drainage pipes and can cause localized health concerns for both fish and people. Nonpoint-source pollution does not originate from a single source but may enter a river at a single location (NatGeo). Storm runoff from roads, household waste water, and agricultural runoff are all examples of nonpoint-source pollution. While the water containing pollutants from these sources may enter a river in many different locations, often times this runoff is collected by storm drains and is released through a single pipe along with treated sewage water. Both point-source and nonpoint-source pollution have the potential to impair the natural process essential to the survival of rivers and streams. Planting vegetation and the key points where pollutants are released can have dramatic effects on the overall health of the waterway. As we consider multiple locations for this riparian vegetation project, it is important to consider which locations allow these plants to trap the optimal level of harmful pollutants.
Restricting or reversing streambank development is often a task that requires extensive community support and considerable legislative prowess, current developments can be made more river-friendly thanks to riparian rain gardens. As mentioned above pollution is one of the major threats facing our rivers. In building directly on the shores of a river, developers recognize the potential for pollution from both construction and the finished building. Because these buildings are much closer to the river, any runoff has much less time to be filtered before entering the water. Planting raingardens between the building and the river can form a much needed barrier that decreases the amount of pollutants that enter the water. These rain gardens can also provide much-needed habitat for the animals that are now displaced by the development.
While erosion and seasonal flooding are natural and beneficial processes, they have been accelerated to an unsustainable rate due to human actions. Climate change certainly plays a role in increased flooding (through more intense storms, faster snow melting periods, and longer wet seasons) but at a local level impermeable surfaces have the most noticeable impact. Impermeable surfaces are essentially any surface where rain cannot drain directly into the soil. This includes roads, roofs, parking lots, sidewalks, and any other asphalt or pavement surface. When rain falls on a permeable surface like soil, it will slowly be absorbed and won’t enter local waterways for a considerable amount of time. During this time the water is filtered and used by plants so the it enters the river or stream more gradually. Alternatively, when water falls on an impervious surface it is generally collected by storm drains and enters the waterways much faster and without any natural filtration. This rapid increase in flowrate can cause local flooding and jeopardizes the livelihoods of people living in the low-elevation areas around the stream. This not only presents a ecological and environmental challenge, but a social justice one as well considering these areas often house poorer ethic minority areas (I may include an example here about a localized flooding directly related to impervious surfaces or a social justice example- which do you all think works best?). This increased flowrate intern exponentially increases the sediment that is eroded away from the river’s banks. This increased erosion completely transforms the downstream landscape and jeopardizes those living directly on the streambanks. Increasing vegetation will not only slow the runoff but also anchor the banks. This anti-erosion approach competes with other methods such as sandbags and stone support structures but will provide a more natural, sustainable, and long lasting solution.
This image displays the effects of increased erosion on river banks (left) and a man-made rock barrier (right)
Not outlined above are the many ecological benefits presented by streambank vegetation. A study conducted in Washington State, USA, concluded that nearly 80% of all wildlife species in the area use riparian habitats at some point during their life cycle (Kings County). Fish, often times one of the most economically important species in an ecosystem, benefit immensely from riparian vegetation. In addition to reducing the suspended sediment in the water that may deter certain fish species, water-side plants offer habitat, breeding grounds, and a food source to fish both directly through edible vegetation and indirectly by promoting healthy insect populations. Additionally, these plants provide habitat and food to birds, small mammals, amphibians, and reptiles, transitioning a previously unhabituated shoreline into an area bursting with biodiversity.
While limited by it’s native climate, mangroves are some of the best options for coastal and riparian vegetation. They provide essential habitat to young fish and sharks as well as crabs, birds, and reptiles. Additionally, mangroves are one of the best options to combat shoreline erosion and damage from storms. Studies suggest that, pound-for-pound, mangroves can sequester four times as much carbon as rainforests can.
Carbon sequestration is another great reason to consider a rain garden or streambank restoration project. Within the scientific community, it is a well-known and excepted fact that the ocean is the world’s greatest carbon sink. A large part of this sequestration ability is attributed to the microbes and algae within the water. Interestingly, many of these microbes can also be found in freshwater and have similar carbon sequestrating properties. In particular, Chlorella Vulgaris, a type of green algae that can be grown in freshwater, has shown in some studies to sequester nearly 400x more carbon than any other plant. While this specific species of algae is exceptional in this right, it proves the potential sequestration capabilities of freshwater. Increasing vegetation and therefore improving the ecosystem of our rivers and streams will promote healthy water quality which, in turn, will allow these powerful microbes to thrive. This approach will allow each and every stream and river to become a weapon against our fight with carbon dioxide emissions.
Lastly, increasing vegetation boarders rivers and streams serves to directly increase the recreational value of that waterway and it’s surrounding green spaces. As mentioned above, riparian vegetation promotes a healthy ecosystem which in turn will support fishing, kayaking, and birdwatching. This direct community-wide impact spreads an overall love for the outdoors and can completely change a drab and boring park into one that is full of life and exploration. This transformative effect is especially impactful when considered in a social-justice light. Within my greater geographic community, as well as in other locations across the US, lower-income areas typically do not have the resources to maintain or improve the health of their natural spaces. Because of historic and systemic discrimination, these areas may even situated around naturally more polluted or less desirable areas and thus have trouble constructing accessible and beneficial green spaces. When choosing how to allocate their resources, riparian vegetation gives them substantial “bang for your buck” because of its extensive yet varied benefits. Treating the parks and natural areas surrounding our waterways with respect will invite members of different social classes to interact and form bonds in different communities.
For my project I examined a local riverside park and identified different areas where increased riparian vegetation would be especially beneficial. As evidenced by the caption below each image, each sites has it own pros and cons. To deal with these inherit differences I considered different plant species and arrangements.
Site 1: Shown in this image is one of several storm drains that lead into a local river that boarders a popular park in the center of my town. While the influx of storm runoff makes it potentially a great place to trap pollutants, the extremely steep bank prevents much vegetation from growing there naturally. Additionally, you can see some erosion directly down stream (right) which would benefit from increased vegetation but at the same time may not handle the foot traffic necessary to plant. For this site I would focus replanting efforts on the banks directly adjacent to the drain as they would still have amble opportunity to catch pollutants while anchoring the soil. Since anchoring is the primary objective of these plants I would recommend deep-rooted shrubs and bushes that are resilient enough to endure lots of storm runoff.
Site 2: This site is located directly downstream from site 1. It shows more pronounced erosion which, over time, may even threaten a road which runs along the the top of the embankment. Additionally, this site is frequently inhabited by waterfowl, because it is less busy than the “park” side of the river, yet they have little to no foliage to hide in or feed from. Similarly to site 1, planting deep rooted and hardy species of bush or even small trees would help anchor the soil. Another strategy to consider involves supplementing live plants with repurposed tree limbs. This provides some more habitat for birds and fish and also can be anchored into the ground, further supporting the soil
Site 3: This site is on the “park side” of the river. Both pictures show the same area but the second one gives a better view of the upstream portion. As you can see in the lower right quadrant of the photo is a small drain which has managed to carve out a small ditch leading to the river. The mud/dirt stretch the boarders the river extends upstream (left) for a total length of around 50 feet (15.2 meters). This area is also frequented by waterfowl and I have seen many fish in the shallow water nearby. The combination of shallow water, ample clear space, and the presence of a drainage pipe make this one of the most promising sites. If possible, I think the ideal replanting approach would be to plant shrubs and bushes around the drain (to filter and slow water flow), small trees along the mud flat area (to anchor soil), and populate the shallow water with reeds, water lilies, and other aquatic plants. Like with Site 2 dead trees could also be used to provide additional habitat to waterfowl and fish while adding extra support to the soil anchoring trees and shrubs.
Thank you so much for reading through my presentation. Please respond in the comment sections your thoughts on the following questions:
- Which site do you think has the most potential and why?
- Where do you see rivers and streams acting as community areas within your neighborhood/city? Are they well maintained and if so, do you think this contributes the their role within your community?
- Do you agree that improving the health and beauty of green spaces in lower-income areas is a form of social justice and helps bridge the class gap?
- Do you fell it is important to have healthy and ecological diverse green spaces in our communities? What role to they play in the development of children?