Theme for 2025:
From Science to Solutions: Preparing for Extreme Weather Events in California

New Orleans 20 Years Later: The Challenges Continue

• Watch the presentation video (slides synchronized with speaker)

Abstract:

[Abstract not available]

Changes in Hurricane Precipiation and Hurricane Helene

• Watch the presentation video (slides synchronized with speaker)

Abstract:

In late September, 2024 Hurricane Helene produced extreme rainfall and flooding in Western North Carolina (WNC). The amounts of rainfall exceeded 1/1000 year amounts from NOAA Atlas 14 in many places. This talk will discuss the precursor rainfall event and rainfall from Hurricane Helene showing the entire radar loop from September 25-27, 2024. The resulting flooding in the Asheville, NC area exceeded the previous flood of record from 1916 when remnants of two tropical cyclones invaded the area within days of each other. Additionally, both historical and projected Intensity-Duration-Frequency curve values for WNC will be discussed and how they compare with observations from Helene.

The Needs of Rural Communities in Times of Emergency: Allensworth, CA, Tulare County

• Watch the presentation video (slides synchronized with speaker)

Abstract:

[Abstract not available]

Perspectives on Updating Probable Maximum Precipitation (PMP) to Account for Climate Variability

• Watch the presentation video (slides synchronized with speaker)

Abstract:

Civil infrastructure design related to managing storms and storm related runoff rely on design estimates of precipitation. For critical infrastructure, this estimate is the probable maximum precipitation (PMP), an estimate of the greatest amount of precipitation that can fall over a given area for a given duration. These estimates are built upon an understanding of the physical drivers of extreme precipitation based on observations of past extreme events. Historically, the PMP estimates have been published in Hydrometeorological Reports (HMRs) which document the considerations made in the estimates provided. The last HMR published for California was number 58/59 back in 1999.

In this talk, I will offer perspectives on drivers of California precipitation extremes at different scales and talk about how a warming world can influence those drivers. Consideration of these factors can help inform methodologies used to estimate future PMP estimates.

Current and Future Intensity-Duration-Frequency Values in the United States

• Watch the presentation video (slides synchronized with speaker)

Abstract:

Rising global temperatures from increasing greenhouse gas concentrations will increase overall atmospheric water vapor concentrations. There is a high level of scientific confidence that this will increase the future intensity and frequency of extreme precipitation events, even in regions where overall precipitation may decrease.

For control of runoff from extreme rainfall, infrastructure engineering utilizes design values of rainfall known as Intensity-Duration-Frequency (IDF) values. Use of the existing IDF values, which are based solely on historical climate records, is likely to lead to under-design of runoff control structures, and associated increased flood damages. However, future changes in IDF values are uncertain and probably regionally variable.

Our paradigm is that changes in IDF values will result from changes in atmospheric capacity (water vapor concentrations) and opportunity (the number and intensity of heavy precipitation-producing storm systems). Relevant storm systems being investigated include extratropical cyclones and their associated fronts, tropical cyclones, and the North American Monsoon system. The overall approach involves developing IDF adjustment factors for changes in these components of the climate system. The adjustment factors have associated uncertainties, primarily from

1. uncertainties in the future pathway of greenhouse gas emissions and
2. variations among climate models in the sensitivity of the climate system to greenhouse gas concentration changes.

In addition to meteorological considerations, the lifetime of projects designed using IDF values is an essential consideration because the IDF values may change substantially during that time.

Flood Challenges in the San Joaquin Basin and the Evolution of the CVFPP

• Watch the presentation video (slides synchronized with speaker)

Abstract:

When we talk about flood challenges in California, the San Joaquin Basin is right at the top of the list. The San Joaquin Basin is one of the most flood-prone and high-stakes regions in all of California. But things are changing fast — faster than our systems were ever built to handle. We're talking about stronger storms, more frequent droughts, land sinking from groundwater pumping, aging levees, and more people and development in harm's way. The infrastructure we rely on wasn't designed for the kinds of extremes we're now seeing. And what's at risk here isn't small. It's people's lives. It's agriculture. It's major water infrastructure. It's the backbone of the Central Valley economy. The San Joaquin Basin has unique challenges including narrow channels and not enough room for water; levees that are aging and vulnerable to future flow scenarios; subsidence; channels that fill up quickly, and communities without the resources or tools to prepare, respond, or bounce back from major flooding.

Responding to some catastrophic events in California and nationwide, voters passed bonds and legislation directing a comprehensive and systemwide look at Central Valley flood issues through the development of the Central Valley Flood Protection Plan (CVFPP). The inaugural CVFPP was published in 2012 and has been updated in 2017, and 2022, following a 5-year update cycle. We are currently working on the 2027 CVFPP update. Each plan has refined our climate change approach, embracing the latest science and hydrology recognizing the San Joaquin Basin could be severely impacted by modeled flow increases of up to 500%.

There is no single management action or project that can build us out of an extreme precipitation level event in the San Joaquin Basin. The CVFPP series has identified critical investment areas where flood risk reduction efforts could also deliver groundwater recharge, habitat restoration, and water supply benefits, reflecting a move toward multi-benefit, adaptive solutions. In the San Joaquin, we've learned that durable resilience doesn't come from levees alone — it comes from vision, coordination, and the courage to lead with both science and equity.

The San Joaquin Basin can either be the epicenter of catastrophic flood risk — or a model for how California can adapt to a changing climate with foresight, coordination, and bold action. We've done the foundational work. We've built partnerships. Now we need to move faster — from planning to execution, from data to decisions, from reacting to anticipating.

San Joaquin River Basin: Watershed Hydrology, Hydraulics, and Flood System

• Watch the presentation video (slides synchronized with speaker)

Abstract:

California is the most populous state in the United States and the third most extensive by area. The Central Valley in California is one of the most productive agricultural regions in the world. The Central Valley watershed comprises over one-third of California's land area that is conveniently divided into three hydrographic regions, from north to south — the Sacramento Valley, the San Joaquin Valley, and the Tulare Lake Basin.

The San Joaquin Valley extends southward, from the Delta to the latitude of Fresno. It is drained by the San Joaquin River, which runs northward from its headwaters in the Southern Sierras to the Delta, with a watershed of about 14,000 square miles and a mean annual runoff of six million acre-feet (MAF). The San Joaquin River hydrologic region has a complex system of levees, weirs, bypasses, and other features that were constructed over the last 160 years by local, State, and federal agencies to manage flood risk. This array of structures, in combination with lands, programs, and modes of operation and maintenance were brought together as the State-federal flood protection system referred to as the State Plan of Flood Control (SPFC). The SPFC relies on many non-SPFC features to function effectively, such as Local reservoirs and levees that help to regulate and coordinate flows into the regions flood conveyance channels, thus reducing the peak load on the system.

Although the SPFC has been instrumental in transforming the San Joaquin Valley into one of them world's most productive agricultural regions and has prevented millions of dollars in flood damages since its construction, flood impacts are likely to continue in the future despite ongoing investments in structural improvements, maintenance, and floodplain management.

Anticipated Climate Driven Changes in Basin Hydrology

• Watch the presentation video (slides synchronized with speaker)

Abstract:

[Abstract not available]

Reducing Stress on the Flood Management System through Forecase Informed Reservoir Operations (FIRO) and Flood-Managed Aquifer Recharge (Flood-MAR), Part 1

• Watch the presentation video (slides synchronized with speaker)

Abstract:

FIRO-MAR operations were developed as part of the Integrated Forecast-Informed Resources Management (I-FIRM) strategy for seven tributary reservoirs in the San Joaquin Basin Flood-MAR Watershed Studies to support benefits for the flood control, water supply, and ecosystem water management sectors. The I-FIRM strategy modifies reservoir operations and establishes a FIRO space to improve management of flood flows, increase applied recharge and establish an eco-pool account to enhance ecosystem management flows and deliveries using stored water in the FIRO space. The FIRO-MAR operations incorporate Ensemble Forecast Operation (EFO) using a 1-to-7-day synthetic ensemble forecast, acknowledging forecast uncertainty. The FIRO-MAR operations consist of two types of new reservoir releases: a conservation space pre-release and a FIRO space release. The FIRO space is sized based upon reservoir characteristics, including gross storage, flood control space, release capacity, and downstream channel capacity. Generally, the controlling factor is how quickly the FIRO space can be evacuated over a 5-day period within downstream channel capacity constraints. The EFO is driven by a risk tolerance curve corresponding to non-exceedance levels of the calculated release. This presentation highlights the main components of operations that strategically combine FIRO and MAR.

Reducing Stress on the Flood Management System through Forecase Informed Reservoir Operations (FIRO) and Flood-Managed Aquifer Recharge (Flood-MAR), Part 2

• Watch the presentation video (slides synchronized with speaker)

Abstract:

The San Joaquin Basin Flood-MAR Watershed Studies evaluates the effectiveness of two Flood-MAR strategies as climate change adaptations for the San Joaquin Basin:

• a streamlined recharge strategy (MAR 90/20), and
• a comprehensive, integrated approach (I-FIRM) that pairs Flood-MAR with Forecast-Informed Reservoir Operations (FIRO).

The results demonstrate that while the MAR 90/20 strategy provides limited water supply benefits through increased groundwater recharge, it offers minimal flood risk reduction. In contrast, the integrated I-FIRM strategy yields significant, multi-sector benefits. I-FIRM substantially reduces flood risk by decreasing the magnitude, frequency, and duration of high-flow events. It also proves more effective for water supply, leading to greater increases in groundwater storage and higher overall groundwater levels compared to the baseline. While reservoir re-operations under I-FIRM may impact salmonid habitat availability, the strategy incorporates enhanced ecosystem management actions to limit these impacts and provide diversified benefits for other indicator species. The findings conclude that a comprehensive, coordinated approach like I-FIRM can create "win-win-win" solutions for water supply, flood management, and ecosystem health, although Flood-MAR alone cannot completely alleviate long-term groundwater overdraft.

Paradise Cut Multi-Benefit Bypass Expansion

• Watch the presentation video (slides synchronized with speaker)

Abstract:

The San Joaquin Valley flood system is already inadequate to meet today's flood risks, and faces a huge escalation in peak flood flows in the coming decades under accepted future climate change scenarios. Risks to lives and property in the San Joaquin Valley are heavily concentrated in the urbanized lower valley, in and around Stockton, Lathrop and Manteca. The Paradise Cut Bypass Expansion and Multi-Benefit Project is intended to reduce these risks under a range of future flows by diverting more floodwater off of the San Joaquin River and reducing flood stages along levees protecting these cities. The project is currently undergoing a feasibility study to identify potential design alternatives and evaluate their performance under potential future San Joaquin River flood flows. This presentation offers a look at certain draft findings of the feasibility study.

Lower San Joaquin Urban Flood Risk Reduction Opportunities and Constraints

• Watch the presentation video (slides synchronized with speaker)

Abstract:

[Abstract not available]

Innovation in Insurance

• Watch the presentation video (slides synchronized with speaker)

Abstract:

[Abstract not available]