The intrinsic beauty of northern California’s San Lorenzo River camouflages the challenges and efforts of maintaining the health of the river ecosystem. The river has been changed, altered, and influenced by people as seen by the presence of levees and dredging operations. Runoff from roads into storm drains carry pollutants and bacteria to the river system sure to degrade water quality.
The Drudgery of Dredgery
The native residents of Santa Cruz knew better than to build permanent structures on the banks of the San Lorenzo River. Spanish settlers learned their lesson and built the Mission and Branciforte Villa on high ground surrounding the San Lorenzo River, using the floodplain only as grazing area for farm animals. But eventually, we made our way down in elevation from the safe high grounds. In fact, downtown Santa Cruz was built right on the banks of the San Lorenzo River and right in the middle of the river’s floodplain.
Ecologically speaking, floodplains are naturally occurring areas that help transport and store flood waters. When a floodplain is developed with homes and businesses it can no longer function as the effective flood relief system nature intended without being a risk to the people that moved in. Due to recurring severe floods, most notably the Christmas Flood of 1955 (read about it here), the Army Corps of Engineers built flood control levees along the urban San Lorenzo River in 1959.
Sediment buildup is common in sections of levees. The segment of the river where the Santa Cruz Riverwalk meets Josephine Street is wider and less steep than portions of the river upstream. When river water hits this area it slows down and deposits sand, silt and clay. For a long time, the levees were maintained with ongoing sediment removal (dredging). The goal was to increase the speed at which water could flow through the river during a flood.
Frequent dredging is costly and is only a temporary fix since sedimentation continuously fills in river beds. The last dredging event occurred in the 1980s. As part of that project, a channel bar in the middle of this portion of the river was built to act as a floodplain and a habitat for riparian vegetation. Since that time, different flood control tactics have been implemented like sediment disking and raising the levees and bridges.
The Water In An Urban River
Think about your neighborhood. Do you ever see someone washing something in the driveway with soap? Do you ever see puddles from oil leaks or an escaped piece of trash blowing in the wind? All of these pollutants from city streets, sidewalks and landscapes are washed into storm drains as it rains polluting your local creek or stream.
Ten storm drains enter the San Lorenzo River. Water runoff from a rain storm can carry these pollutants that eventually affect water quality. Pollution of this type is called non-point source pollution because it is not from a single point like a factory, but a myriad of sources throughout the watershed.
Also affecting the San Lorenzo’s water quality is sediment. Sediment is made up of fine particles such as dirt, clay, silt, decaying plant matter and even decomposing aquatic insects. Large sources of sediment come from erosion that exposes soil along the sides of creeks and rivers. Sediment in water makes it difficult for fish and other aquatic insects to breathe, as suspended sediments can clog the gills of fish. If you’ve ever experienced smog in the air, it’s like this for fish, but worse. As the sediment settles it can bury gravel beds and smother fish eggs and aquatic insects. Cloudy water also diffuses light and heats up the river water.
Bacteria in the river can come from multiple sources such as failing septic systems, leaky sewer lines, pet waste and wildlife. High levels of bacteria have the potential to be harmful to those who come in contact with it. Keep reading to find out how the San Lorenzo River Alliance is working to figure out what is the source of the bacteria in the San Lorenzo.
In the San Lorenzo River, nutrient pollution can come from runoff from lawns and fields containing fertilizers, animal waste, wash water, leaking sewer lines, failing septic systems and excessive dumping of vegetative material. Nutrients are necessary for healthy plant growth, but too much can lead to algal blooms that deplete oxygen in water.
Currently, the San Lorenzo River does not meet some federal and state water quality objectives nor does it support some beneficial public uses including swimming, fishing, use as drinking water or irrigation. What this means is you can’t swim in the river and that public utilities have to work harder to clean up the water before it makes it to your tap. Also, compromised fish habitats may mean less fish in the river.
A Cleaner River than You Might Think
Knowing the source of the pollutants in the San Lorenzo River is the first step to working to reduce them. Working together, the San Lorenzo River Alliance’s Water Quality Working Group is using cutting-edge techniques to find out the source of bacteria in the San Lorenzo River and reduce it. Volunteer to support this project here.
Bacteria are everywhere including the environment and in our bodies. Many of them are beneficial; some are not. Epidemiologists recognize bacteria from humans as posing high threats to public health, but traditional tests required of municipalities can’t tell scientists the origin of bacteria found in rivers and creeks. The San Lorenzo River has historically record high levels of fecal indicator bacteria. However, the question arises as to how much of it is influenced by human input?
The Coastal Watershed Council and the San Lorenzo River Alliance released a technical memo in June 2015 indicating little to no human contribution to bacteria levels in the lower San Lorenzo River. Results from the six months of testing from May to October 2014 showed that bacteria associated with human sewage was rarely if ever present. Additional testing is warranted to verify these results under varying conditions, but the findings represent a challenge to the notion held by many that the river and watershed supplying including two-thirds of Santa Cruz’s drinking water are badly polluted.
The report details the efforts of eighteen months of work by the San Lorenzo River Alliance’s Water Quality Working Group, including the City and County of Santa Cruz, the Surfrider Foundation Santa Cruz Chapter, the Central Coast Regional Water Quality Control Board and CWC. The working group tested for specific sewage-associated chemical and microbiological constituents to learn more useful information, with the intention of identifying and addressing human sources of bacteria in the watershed. The group plans to repeat the study during regular, non-drought conditions and will need volunteers like you to help! Sign up today here.
Learn more about the work of the Coastal Watershed Council and the San Lorenzo River Alliance here.
Take the Self-Guided Mobile Tour
This piece is part of the San Lorenzo River Tour by the Coastal Watershed Council. Download the free app with many tours of the Santa Cruz area and beyond.
Sources Used
- San Lorenzo Urban River Plan. City of Santa Cruz. June 24, 2003.
- Flood Control Failure: San Lorenzo River. Gary B. Griggs, Lance Paris. Environmental Management. 1982. Volume 6, Issue 5,pp 407-419.
About The Author
It seems urban freshwater river systems are often a casualty of industrialisation sadly.
In Sydney Australia we’ve had a similar experience with our ‘Tank Stream’. It was once a thriving little river that nourished the local Indigenous population for tens of thousands of years. Due to irresponsible and short sighted environmental management however within a couple of decades after European settlement it had became an open sewer. After a few decades it was covered over with stone slabs and more or less forgotten about. More: http://tankstream.org.au/history
I think there is a growing appreciation among policy makers and the broader community about the importance of river habitat conservation in our urban centres though. The experience of South Korean in restoring the Cheonggyecheon River show whats possible once the public mind has been mobilised.
Enjoy your blog, thank you ~ Claude