Q&A: What Will It Take to Prevent Another Coyote Creek Flood?

Q&A: What Will It Take to Prevent Another Coyote Creek Flood?

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Editor’s Note: On the morning of February 21, the Rock Springs area of San Jose saw the city’s worst flooding in two decades when winter storms caused Coyote Creek to overflow. Early storms this year had saturated watersheds, and increased runoff from subsequent storms caused the creek to rise dramatically. The City of San Jose failed to warn residents, with city officials saying they’d been given inaccurate information by the Santa Clara Valley Water District. Nearly 15,000 people had to be evacuated. NAM spoke with John Varela, the board director of the water district.

What is the major lesson learned for the District from last month's catastrophic Coyote Creek flood?

The water district understands the need to have a strong collaboration with the City of San Jose and other cities to reduce flood risk to residents. The district and city are developing a joint emergency action plan with specific thresholds and defined corresponding actions.

What is the likelihood that a similar flood could recur, and what steps is the District taking to ensure there will be advance warning if it does?

The type of storm we saw on President’s Day was classified as a 20- or 25-year storm event. We haven’t seen similar flows in Coyote Creek since 1997. However, that doesn’t mean that we won’t see flooding for another 20 years. With any chance of storm, parts of our county are susceptible to flooding … There are about 66,000 parcels that are in the FEMA flood zone. We are working every year to reduce that number, but the flood risk will continue to exist. People should be aware that not all flooding can be predicted. Our ability to forecast stream flows is improving, but it’s not a perfect science. Strong downpours can cause streams to rise quickly, and flash flooding can happen quickly and without warning.

The district will continue working with cities and regional partners to communicate and to ensure understanding of existing flood risks and work on developing joint emergency action plans to improve inter-agency communication.

The City of San Jose has criticized the district for inaccurate data regarding channel capacity and flawed estimates of flood risk. What is the District’s response?

The water district followed the procedures and protocols and provided the necessary information and data to the City to notify residents that flooding was imminent in the President’s Day storm event. Numerous indications showed the potential for flooding at vulnerable areas along the creek. Given unpredictable variables with a natural creek like Coyote, our estimates were within a standard range … The City was aware of the forecast predicting flooding from the National Weather Service, and from a technical and professional standpoint, should have been relying on all the data that was presented, rather than basing its actions on one single piece of data [i.e., the flow rates in Coyote Creek].

The District is not responsible for calling for evacuations. However, a period of 24 to 48 hours is likely appropriate to facilitate a timely and orderly evacuation. It’s unclear what trigger the City of San Jose was using for its evacuation decisions. If it was only flow rates in Coyote Creek, that obviously would not have allowed for a timely and orderly evaluation. In fact, it would have only provided for a maximum notice of 4 to 6 hours for the impacted communities.

What is the district doing to improve its flood monitoring protocols?

Our hydrology team is working on further developing an existing flood forecasting tool to extend monitoring and forecasting to other parts of our county, including Coyote Creek. This tool is a useful resource in sharing information with partner agencies. A byproduct of the flood is that we now have a more current estimate of where flooding occurs along Coyote Creek and the estimated flow levels. Previous estimates were based on flows from 1997 storms, the last recorded high flow event in the creek, in addition to a field study that measured the shape of the channel. Over the course of 20 years, there are a variety of factors that can impact the capacity of the creek. Creeks can extend in a different direction, erosion can occur along the creek, and vegetation growth and creek blockages can also occur over time.

What steps can residents take to protect themselves from future flooding?

Disaster preparedness is key, not just for flood safety but for any naturally occurring disaster. According to FEMA, 83 percent of Americans do not consider themselves prepared for an emergency. So it is crucial for residents to be prepared with emergency supplies at home, at work, and in their car, and that they have an emergency evacuation plan with their families. Also key for flood safety is being aware of your flood risk. Residents should be aware of the location of neighborhood streams and know how to get to higher ground in the event of flooding. Another important action that residents can take is purchasing flood insurance, which can save a lot of headaches and money; most homeowners and renters insurance do not cover flood damage. The water district has flood protection resources available on our website, www.valleywater.org.

What message does the District want to send about its role?

In the last four decades, the water district has invested more than a billion dollars in reducing flood risk, protecting more than 93,000 properties in previously flood-prone areas. However, flood risk still exists in our county, and with more than 60,000 parcels in the FEMA-designated floodplain, we currently have 18 projects underway to reduce this risk. Flood protection projects are large and multifaceted undertakings … Support from the community and agencies at the local, state, and even federal levels is crucial for a successful project. The water district will host a series of post-flood community meetings to analyze the event and how we can leverage community relationships, agency partnerships, and resources to reduce flood risk in the future.