Coyote Creek Flood Preliminary After Action Report. March 9, 2017

Transcription

1 Coyote Creek Flood Preliminary After Action Report March 9, 2017

2 I. What Happened

3 Lower spillway waterfall at Anderson Reservoir Feb. 18: Anderson Reservoir reached capacity for the first time since 2006 Feb. 21: Coyote Creek flooded three regions of San José Photo credit: Len Ramirez/KPIX

4 Anderson Dam and Reservoir (pictured in 1995) Photo credit: Santa Clara Valley Water District Location: Morgan Hill Capacity: 89,073 acre-feet Operated by the Santa Clara Valley Water District The district is responsible for flood protection in Santa Clara County

5 Coyote Creek flows northwest from Anderson Reservoir to San Francisco Bay The creek passes through Morgan Hill, San José and Milpitas Water flooded homes in Rock Springs, Greater Downtown, and Berryessa

6 Anderson Dam outlet The district is required to keep storage at or below 68% for seismic safety Jan. 9: The district sets outlet pipe to full release (400 cfs) to drain reservoir Jan. 22: The reservoir climbed above 68% amid heavy rainfall Photo credit: Nhat Meyer/Bay Area News Group

7 What Happened Key Insights Rainiest season in 20 years Anderson reservoir was full Local rain event was about a 3-year storm Anderson spill led to 100-year flood condition in Coyote corridor City storm collection system functioned as designed

8 Tools for Decision making Weather reports provided by the National Weather Service Coyote Creek Channel Capacity Table and Map provided by SCVWD Channel flow projections (peak flow estimates and arrival times) provided by the SCVWD Actual flow data provided by SCVWD flow gauges, reported on the SCVWD website Field reports provided by City staff

9 Coyote Creek Channel Capacity/SCVWD (Memo Attachment 2)

10 Flood Event Timeline (Memo Attachment 3)

11 Flood Event Timeline

12 Flood Event Timeline

13 Rock Springs Channel capacity: 7,400 cfs per SCVWD Actual flood occurred at 4,500 cfs Flow overbanked at multiple locations Collection system filled by overbanking and backflow from outlets

14 Rock Springs Inundation Map

15 William Street Park and Selma Olinder Neighborhood Channel Capacity: 11,510 cfs per SCVWD Actual flood occurred at 5,500 cfs Flow overbanked generally throughout the area Where outfall flapgates present, collection system closed, but filled by overbank water Collection system also filled by backflow where no outfall flapgate present

16 William St Area Inundation Map

17 Five Wounds Neighborhood Elevated flows in creek likely caused by large fallen tree Collection system filled by outfall backflow

18 Santa Clara Inundation Map

19 Oakland Road Mobile Home Parks Updated channel capacity from SCVWD: 10,000 cfs South end of levee overbanked and circumvented at approximately 3,517 cfs (previous SCVWD provided capacity) All three parks flooded by creek overbanking

20 Mobile Home Parks Inundation Map

21 II. Summary Insights

22 1. City accepts responsibility for not giving adequate and timely notice to San José residents and businesses about the potential for flooding on Coyote Creek and the need to evacuate. 2. City relied on SCVWD data that was fundamentally flawed. 3. The City and SCVWD must improve early warning notifications so that residents can better prepare for potential flooding and evacuation. 4. City did not have effective means to communicate in a timely manner with our most vulnerable residents. 5. The City immediately planned and executed an effective, multifaceted recovery process following the flood to make sure this doesn t happen again 6. SCVWD must accept responsibility to protect the communities of Santa Clara County from floodwater and stormwater in the district.

23 III. Better Notification

24 Preliminary Insights Did not give early alert of potential flooding that could require evacuation Lacked language skills or instant translation Need basic methods to reach vulnerable populations, people who don t speak English, or don t use mobile devices/internet Need mass notification system that serves diverse residents

25 Immediate Improvements: what we ve done Improved use of AlertSCC and the Emergency Alert System Developed initiation and escalation thresholds for notification Updated Warning and Evacuation alerts in three languages Purchased Long-Range Acoustical Device and preprogrammed messages in multiple languages Restructured and expanded EPIO staffing Developing door-to-door outreach New procedures to assess neighborhood communications needs and channels

26 Other Recommendations: what we ll do next Develop a comprehensive, layered approach to emergency mass notifications, that includes ways to reach a variety of people through both basic and technology-based methods. Pre-identify community institutions/networks in various geographic areas that can assist with emergency notification and recovery Partner with Santa Clara County as they transition the Alert SCC System to a new emergency mass notification application Develop a system for notifying San José businesses of emergencies notification, including during off-hours Purchase additional long-range acoustical devices (LRADs) to deliver targeted, multilingual emergency messaging in neighborhoods Put options in place to more quickly deploy bilingual-certified staff during emergencies and potential emergencies for outreach and translation Expand the City s inventory of ready-made emergency messages in the languages most commonly used in San José for the most common emergencies.

27 IV. Better Stormwater Monitoring/ Decision-Making Protocols

28 Preliminary Insights SCVWD Channel Capacity data proved flawed; can t be used to predict flooding which would occur shortly after channel capacity exceeded Rock Springs flooded at two-thirds of stated channel capacity; William Street Area at about half SCVWD estimates of travel time from peak spillover to San Jose neighborhoods were revised Based on information provided by SCVWD, the City decided to initiate evacuation notice in Rock Springs Tuesday morning for anticipated flooding to start around 6:00 p.m. Tuesday Flood came suddenly at about 9:30 a.m. Tuesday

29 Immediate Improvement: Flood Threat Matrix Considers measurable data: Reservoir levels River stage heights and flow levels Flow trends (raising, peaking, receding) Flow travel times Field observation Data trigger three threat levels: Level 1 - Yellow: Flood Advisory possible flooding Level 2 - Orange: Flood Warning flooding likely Level 3 - Red: Flood Evacuation flooding imminent

30 Other Recommendations: what we ll do next Work with the SCVWD to complete the Flood Threat Matrix tool for advising where and when to send community notifications. Coordinate the triggers and levels of alerts with the SCVWD, County Office of Emergency Services, NWS and other flood emergency agencies. Develop and implement flood water monitoring tools for field and engineering staff to use when making recommendations for community notifications. Work with the SCVWD to prioritize stream maintenance activities to occur during the dry season. Develop a list of near-term improvements, and funding priorities to include in the Proposed Budget for implementation this summer. Work with the SCVWD to develop an Emergency Action Plan for the Coyote Creek.

31 V. Better Flood Protection and Prevention

32 Preliminary Insights Core solution: better flood prevention and protection Greatest contributing factor in flood event: Anderson Reservoir spilled over; prior releases this season were insufficient SCVWD committed to flood channel improvement in 2000 and 2012 parcel tax measures; must occur Principal responsibility for maintaining creek channels for floodwater conveyance lies with SCVWD Although property in and alongside creek has many owners, planning and coordination for channel maintenance is led by SCVWD in its role as the local flood control agency

33 Recommendations Work with the SCVWD to: ensure sandbags are readily available at convenient locations to residents and businesses in neighborhoods that flooded put in place interim improvements along Coyote Creek, such as installing temporary flood walls near Rock Springs implement flood protection improvements along Coyote Creek in San José implement solutions for ongoing channel maintenance accelerate the Anderson Dam Seismic Retrofit project to improve safety for San José residents

34 VII. Recovery Update

35 WHAT HAVE WE BEEN DOING? Meeting the needs and providing safety to flood survivors Communication that is open, candid, and direct Operating as a team

36 IMPACTED NEIGHBORHOODS Rock Springs Neighborhood 505 units cleared for reentry and 30 units have restricted entry Intense street cleanup began Wednesday and continued through Friday March 3 Street and debris cleaning and daily patrol is ongoing Near William St: Naglee Park, Brookwood Terrace, Olinder, and Five Wounds neighborhoods 3,054 units cleared for reentry; 113 units have restricted reentry; one unit is red-tagged Street and debris cleaning and daily patrol is ongoing

37 IMPACTED NEIGHBORHOODS Old Oakland Rd, Golden Wheel, South Bay, Riverbend Mobile Home parks All units have been cleared for reentry Street cleaning & debris is ongoing Water service now fully restored Spartan / Keyes Neighborhood All units have been cleared for reentry

38 EMERGENCY SHELTER / LOCAL ASSISTANCE CENTER (LAC) 200 people are using the shelter LAC provides a one-stop multiagency assistance center with approx. 20 support organizations LAC is a safe place for affected residents, regardless of immigration status LAC provided service to 1,886 households

39 ONGOING RECOVERY EFFORT Continued services & resources provided through Mini LAC at City Hall Public safety have continued to provide high level service to impacted areas To date, more than 4,000 volunteers checked-in to help with recovery and cleanup More than $6 million has been raised for the San Jose Flood Victims set up by the Silicon Valley Community Foundation

40 Joint Meeting: San Jose City Council SCVWD Board of Directors Friday, April 28 9:00 a.m. - Noon