Aug 13, 2021

Photograph Friday: drought and big storms around the Morro Bay estuary

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Today, we’re sharing photos that depict drought and large storms, two extremes that are expected to occur more frequently on California’s central coast due to climate change.

Historic drought

The 2021 water year, which began on October 1, 2020, has been historically dry. The California Department of Water Resources expressed concern about the dry winter conditions back in January 2021. In his Weather Watch column, John Lindsey tackled the future of drought across the state in June 2021, and the Central Coast’s quick dive from a state of Severe Drought to Extreme Drought in July 2021.

Brown hills lead down to the bay in this photograph taken from the upper reaches of Chorro Creek.
Brown hills lead down to the bay in this photograph taken from the upper reaches of Chorro Creek.
Certain creeks in the Morro Bay watershed have year-round flow, while others, like this site along Dairy Creek, go completely dry in the summer.
Certain creeks in the Morro Bay watershed have year-round flow, while others, like this site along Dairy Creek, go completely dry in the summer. During extended droughts, more creeks are likely to go dry during the summer.

Big storms

Despite the overall dry conditions, we also saw a large storm in January that dropped as much as 13 inches of rain at Rocky Butte and more than eight inches in Los Osos.

This photograph from February of 2021 shows South Bay Boulevard flooded from heavy rains.
This photograph from February of 2021 shows South Bay Boulevard flooded from heavy rains.

This video from the San Luis Obispo Tribune shows San Luis Creek’s low water level before the storm and it’s rapid rise and rush as the storm progressed.

Storms of this magnitude are not unheard of, but we don’t expect to see them very often. In fact, the January 2021 storm has been called a 10-year storm event, meaning that we can expect to see a storm that large only once every ten years. (This doesn’t mean a storm this large can’t happen more frequently. The United States Department of Agriculture explains how “storm recurrence intervals”—10-year and 100-year storm sizes, for example—are calculated.)

Increased drought and storminess

Unfortunately, scientists expect this combination of drought and big storm events to become much less remarkable on California’s Central Coast as a result of climate change.

In this photograph from 2019, heavy rains caused Chorro Creek to top the bridge at Canet Road. With climate change, we expect that the Morro Bay area will receive less overall precipitation and that the storms we do experience will be more intense.
In this photograph from 2019, heavy rains caused Chorro Creek to top the bridge at Canet Road. With climate change, we expect that the Morro Bay area will receive less overall precipitation and that the storms we do experience will be more intense.
In the heavy rains of March 2018, the willows and other plants in the restored flood plain at Twin Bridges along with the wide expanse of salt marsh at the waters edge gave the rushing runoff a place to slow down and sink in. Without these natural spaces, flood waters continue on toward the bay in full force and the possibility of increased erosion and damage to infrastructure rises.
In the heavy rains of March 2018, the willows and other plants in the restored flood plain at Twin Bridges along with the wide expanse of salt marsh at the waters edge gave the rushing runoff a place to slow down and sink in. Without these natural spaces, flood waters continue on toward the bay in full force and the possibility of increased erosion and damage to infrastructure rises.

Our Climate Vulnerability Assessment for the Morro Bay watershed shares more information about how we can expect our climate to change in the coming decades.

Healthy creeks, marshes, and floodplains can help

Healthy creeks, marshes, and floodplains can help protect both our natural areas and infrastructure—like roads, bridges, and buildings—from both drought and runoff from large storms.

Floodplains, the areas of land directly next to flowing creeks, allow water to spill over the banks, slow down, and sink into the soil instead of flowing downstream.

Chorro Creek Ecological Reserve Floodplain
In 2020, the Estuary Program and partners completed an extensive floodplain restoration project at the Chorro Creek Ecological Reserve. Here, you can see the floodplain hard at work after the January 2021 storms. 

When trees, shrubs, and other vegetation line creeks and dot floodplains, their roots tunnel through the soil, making room for water to sink in. The foliage, trunks, and branches of these plants intercept rainwater before it hits the ground. This slows the water down, making it more likely that the water will percolate into the ground rather than rushing over it.

While we are always excited to get out into our creeks, we doubly appreciated it this year. The surveys were a chance for us to venture out of our makeshift home offices and served as a good reminder of why we do the work that we do.
The vegetation in and around this creek will slow and help to sink rainfall, reducing runoff and the threat of flooding.

Marshes, including Morro Bay’s salt marsh, act like a sponge. During storms, they can hold onto excess water, preventing it from damaging other habitats and infrastructure. Wetlands also hold onto water during dry times, releasing it slowly and allowing the plants there to live even when water is scarce.

This photograph, courtesy of Ruth Ann Angus, shows the salt marsh during a King Tide.
This photograph, courtesy of Ruth Ann Angus, shows the salt marsh during a King Tide. King Tides are the highest tides of the year and can give us a glimpse of the everyday high tides that we can expect to see with sea level rise.

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