The Sacramento Weir directs water from the Sacramento River through the Sacramento Bypass Wildlife Area and into the Yolo Bypass in 2017. Photo by Florence Low / DWR

CA WATER COMMISSION: Headwaters to Floodplains initiative

Recently, the Department of Water Resources, Office of Floodplain Management launched a new safety initiative called Headwaters to Floodplains which applies an integrated regional watershed management approach to the realm of flood management.  The initiative is intended to enhance public engagement and facilitate sharing innovative flood risk reduction ideas and projects on a watershed basis.

At the January meeting of the California Water Commission, Mike Mierzwa from DWR’s Office of Floodplain Management briefed the Commission members on the new initiative.  He is a civil engineer with extensive expertise in hydrodynamic modeling and the planning of large scale water systems.  He’s also been part of DWR team working on the public benefits for the Water Storage Investment Program.

Mr. Mierzwa began by noting that headwaters and floodplains are places where Californians live and work. “We’re focused in on the land use connectivity with flood risk and consequences and the cooperation, so if there’s one key thing I could stress today, it’s this theme of cooperation at all levels of government as to how we manage flood risks.”


He presented a graphic from the 2013 report, California’s Flood Future, a report which solicited input from over 100 flood management agencies across the state of California to identify flood risk exposure, the flood hazard types, and the plans for mitigating that risk.  The graphic on the lower left shows the ten hydrologic regions and the types of flood hazards for that region.

One in five Californians are exposed to flood risk, a statistic from of a simple analysis of where people live.  He noted that most Californians either work within floodplains, transit on their commute from home to work through floodplains, or depend upon floodplains for commerce and other activities, so all of California is physically at risk due to flooding.  Out of the 7 million Californians in 2010 that were living within floodplains, the majority of them were living within the South Coast region.  The #1 county that has both the greatest financial exposure and population exposure is actually Orange County, he said.

There are over 20 sensitive species that are living and exposed to flooding within the state of California.

All 58 counties are at risk for flooding, albeit in different ways.  Flood management systems along the coast have been predicated for tsunami and coastal flooding events; in the Central Valley, there are engineered levee failure flood hazards as well as the slow rise flooding; and in Southern California, there are the debris flows and alluvial fan flooding.

The estimate of assets physically exposed to flooding in 2013 was roughly $600 billion (or half a trillion dollars); an updated estimate puts that closer to $800 billion.   As the state economy improves, that estimate will continue to rise; it’s also tied to census data so as that data is collected, they will update their population numbers for those living within the floodplains other baseline data.  Flood exposure is very heavily weighted for the physical assets within Southern California; however, the San Francisco Bay hydrologic region is urbanized and also has a high exposure to the property as well as life loss.

The challenge we have with population growth and climate change is some of the infrastructures and ways that we have been addressing flood management on a regional basis are changing, and solutions that work in one part of the state now have lessons that can be learned and shared within other parts of the state as we manage an unfortunately growing hazard portfolio,” said Mr. Mierzwa.  “We have solutions and the opportunity to work with others within the state try approaches that work for hazards in other areas.

There are flood risks to the state’s agricultural economy.  The flood season typically runs from mid-October through mid-April; however, with climate change, that flood season is actually extending, he said.  Significant rain events are occurring earlier into October as well as later into season and that extended flood season impacts agricultural productivity within the state.

2017 was a record year where we had a flood emergency operations center that lasted all the way through the end of June of 2017 just to the heightened change of what’s happening with climate change,” he said.  “Most people don’t understand that farmers count on the winter months to not only grow winter crops, but provide a lot of maintenance on their land, so they need access.  the flooding that happens within the flood season can have significant impacts on agricultural activities.   California is the top agricultural producing state within the US and within regions of the world, so we literally are the food bank for the planet, and when you get into the Central Valley, the area where we have pronounced flood risk; you’re looking at Fresno, Tulare, and San Joaquin counties exposure just for the loss of crops – each of them is ranging from a half billion dollars to a billion dollars in flood risk exposure.”

Mr. Mierzwa pointed out that there are a number of challenges.  The infrastructure we rely on to protect ourselves from flooding is aging, the state’s population is growing, and people are moving into these floodplain areas that are at risk, as well as the land use within these floodplains is intensifying, and all of this puts pressure on all of the systems.

We updated the Flood Future report’s information around 2018, and talked about flood risk to an additional 100 water management agencies, so a collection of 200 water management agencies, and they all pointed out that there is insufficient funding and a lack of technical resources to perform operations and maintenance, as well as to support new flood risk reduction projects,” he said.  “The key to all of this is that flooding is a very local phenomenon, and it is not a one size fits all approach.  While there are lessons to be shared and learned out there, what’s successful in one part of the state might not be successful in another.


The climate change impacts of less snowpack and more intense rainfall in shorter time periods means higher peaks and that combined with rising sea levels has exacerbated flood risk across the state.  With that in mind, in 2017 the DWR established the Headwaters to Floodplains Flood Safety Partnership which is a collaborative partnership amongst public agencies at the local, federal, and state levels with the focus and mission to reduce exposure to flood risk and reduce the consequences of flooding.

This partnership is focused on strengthening cooperation and data sharing; the funding is already in place, so it’s not necessarily about getting new funding but more about smarter ways to apply that funding to address flood risks as well as identifying and addressing the unmet needs, he said.

The Headwaters to Floodplains initiative does not replace existing programs or projects, but rather strives to make these efforts more effective.  “We’re not replacing anything, but basically by sharing information, we’re increasing our efficiencies,” he said.

Members of the partnership include both the Flood Management and Dam Safety programs at the Department of Water Resources, the California Office of Emergency Services, and the Federal Emergency Management Agency’s risk management team based out of FEMA Region 9 headquarters in Oakland.  They meet on a monthly basis and have been working on developing the work plans and governance structures to begin outreach to get more participation for local agencies, communities and other state agencies.

The value of the partnership is that traditionally, jurisdictions are limited to actually spending their investments and money and actions within their boundaries; however, the Sacramento Area Flood Control Agency has recognized the opportunity to protect Sacramentans and others within their special district by engaging in partnerships and investing in areas upstream of the city of Sacramento.

This is something we’re trying to emulate statewide through this headwaters to floodplains flood safety partnership,” Mr. Mierzwa said.  “It’s to pull together various local agencies so they can come up with comprehensive solutions to addressing flood risks.  We take a full watershed approach, we look at literally the headwaters, the dams and reservoirs that are a critical part of our flood management infrastructure as well as the floodplains themselves as a place where water would naturally go, and recognizing all of the various land uses from environmental, to agriculture, to recreational, to urban and suburban settings, and all of that is what we’re bringing together to come up with our collaborative solutions.”

Flooded Yolo Bypass. Photo by Steve Martarano, USFWS (ret)


The graphic on the slide is a stairstep graphic that depicts the buying down of risk that was developed by the US Army Corps of Engineers back in 1990s to communicate to people that there is always a flood risk associated with everything, Mr. Mierzwa said.

The word flood control is something we don’t speak of anymore because we can’t control floods but we manage the risk,” he said.  “The concept here is that on the vertical axis, going up and down, is the relative measure of the risk of flooding for any location, and as you move across the bottom of the graphic, you go through risk assessment, planning and preparedness investments, and eventually response and recovery activities that literally buy down your risk.  The key message is that there’s no one silver bullet to managing flood risks in the state of California, but it takes a comprehensive set of actions, and the headwaters to floodplains partnership is about recognizing what that set of actions are and actually becoming advocates for the effective implementation of that entire suite of actions.”

The stars on the graphic indicate activities that are low-cost and easy to achieve on a timely basis.  The first is emergency management planning; there’s a lot of value in having emergency response plans, conducting table top and functional exercises, having call trees, and the emergency action plans that are required for state and federal dams – those are all tools and resources that when a flood occurs, they can be implemented to reduce the losses.

The next step is the traditional floodplain management activities which include land use planning, building codes and zoning, considering retreat as an option in areas where there are increased risks, land acquisition, and easements, and the development of risk-based tools so that we can actually track the change in the risk over time.  Mr. Mierzwa noted that it’s not listed on the slide, but there are also federal and state programs to elevate and raise structures.

There is an idea to have a flood insurance program within the state of California that would be an alternative to the National Flood Insurance Program – not a replacement, but an option.  That idea was adopted as a recommendation by the Central Valley Flood Protection Board in 2017 because California effectively is a donor state to the National Flood Insurance Program; with the increasing storm frequencies and intensities, particularly around the Gulf Coast, Californians pay more into the National Flood Insurance as individuals then they get back in the claims that are put in through the program.

The next step is reservoir/floodplain storage operation, which is utilizing both surface storage and groundwater storage, as well as promoting Forecast Informed Reservoir Operations (FIRO) where we make better use of forecasts, and information and data collection to go through and optimize that balance between water storage and flood operations.

The Department was engaged in FIRO operations in the San Joaquin Valley in 2017, and while there was flooding across the entire state, Mr. Mierzwa attributed the non-losses on the San Joaquin to effective coordination amongst multiple reservoir operators, the Army Corps of Engineers, the National Weather Service, Cal OES, FEMA, DWR, and all of these local water management agencies.

It’s a true success story,” he said.  “They went through and had weekly coordination phone calls on the front and back end of the event, and when they were having peak flows into the system, they would have daily coordination calls.”

The next two steps, operations and maintenance and the development of structural solutions to flood management, such as the flood infrastructure, levees, channel improvements, bypasses, culverts, pipelines – these are not the focus of the Headwaters to Floodplain initiative because there are existing state programs already focused on that, he said.  However, while not the major focus, they do have a touchpoint in buying down risk in the partnership.

The last step is emergency management, which includes both the response actions during the event as well as the recovery actions.   The recovery actions are particularly important for taking the lessons learned from a flood event and applying those on the front end to new infrastructure investments that are made.


The Headwaters to Floodplains partnership is about cooperation.  It is not meant to replace direct engagement with the public or replace any existing agency.  Rather, they are trying to provide a venue for frequent, informal coordination.

There will be disagreements between agencies, that’s just a fact of life,” he said.  “However, by having a safe place to have conceptual discussions and learn from successes and failures, we truly believe we’ll have the opportunity avoid misunderstandings and come up with better solutions.”

This initiative is not aiming to change existing policies or administrative procedures, but there will be the opportunity to explore new approaches to the existing policies and discuss possible policy changes.  He gave the example, noting that FEMA in the administration of the National Flood Insurance Program has a way to calculate the risk which is a factor in what the insurance premium is for an individual property.  FEMA has some discretionary authority at headquarters on how they administer that risk.  So not a legal or policy change, but there is an opportunity for states and floodplain managers to have discussions and give that recommendations and solutions to FEMA that could make flood insurance more affordable for Californians.

The partnership would not replace funding decisions; however, understanding when there is an opportunity to comment on guidelines and submit project solicitation proposals is invaluable.  There’s also availability for some technical assistance, he said.

The partnership isn’t changing any agency roles.  There are regulators, implementers, operators, and maintainers that are all participating, providing an opportunity to have shared innovations, experiences, and collaboration.

“The review process and internal policies of participating agencies are not something that we’re really wanting to change, but understanding how long it takes for agencies to make decisions can actually streamline and help you schedule when you’re going to work through a permitting process or when you can go through and count on financial assistance from the program,” he said.  “The chain of command and authorities will continue to exist and be increasingly aligned through participation.”

Colusa Weir releases overflow waters of the Sacramento River into the Butte Basin in  March, 2019.
Photo by Zack Cunningham / DWR


The Headwaters to Floodplains initiative is built around three cornerstones:  Engagement, technical assistance, and funding assistance.


One of the benefits they are hoping to achieve through collaboration is to facilitate consistent messaging, Mr. Mierzwa said.  If in their outreach to the public, all 200 participating agencies are stating the exposure is 1 in 5 Californians, the will start to sink in, and the next generation of Californians will be more aware of their risk.

They want to strengthen collaboration amongst dam owners.  He reminded that legislation passed following the Oroville Dam incident required the state to develop a database and website where the public could view dam inundation maps for the state-regulated dams, and then promulgate that information to the local community so when they are developing or growing, that they have an awareness of where that risk is.   Other outreach efforts includes webpages, partner meetings, newsletters, presentations, and informal materials.

FEMA has a robust website with a lot of information and best practices; however, he acknowledged it’s so robust, it’s easy to get lost in their information, so there’s value in having a floodplain manager walk you through that process.

We’re not replacing anything but streamlining people’s access to information,” he said.

Technical assistance

The Department is interested in creating and sharing the technical tools.  Mr. Mierzwa said they have a library of flood models that anybody can add the model they develop making it available for others to use, which saves some development costs and reduces redundant modeling efforts.

“This is not just having a static library of models out there, but actually having librarians that can help guide people through the process of making use of these models,” he said.  “We want to enhance the local agency staff, capacity, and capabilities.  This is the most important thing.”

They are also very interested in expanding weather monitoring activities across the state and developing a master plan of what the data gauging need is.

In the Governor’s Water Resilience Portfolio, proposal 25 focuses on flood risk management, with sub activities 25.2, 25.4, 25.5 and 25.6 all being heavily related towards the value provided by technical assistance, he said.

What I’m proposing is that we could utilize this particular partnership to inform the development and the administration’s response to implement some of those proposals,” he said.

Actions 25.4, 25.5 and 25.6 are about enhancing the local and state hazard mitigation plans which are required by the Stafford Act of 1988 to be updated every 5 years.  Those plans are supposed to include a comprehensive list of future investments and actions that the agency wants to take to mitigate any risk, such as flood risk, drought risk, fires, or earthquakes.

The value there is that the information is existing and we’re trying to connect that information with the integrated regional watershed management plans, the Sustainable Groundwater Management Plans, and the water use efficiency plans across the state, and start practicing integrated water resources management by utilizing our authorities as emergency responders to get some of that information into the hazard mitigation plans, as well as to take information from the hazard mitigation plans and share that with these other planning efforts.  The idea there is that if we can go through and identify the partners that are proposing in one plan versus the other, we can get more cost share partners and have more funding opportunities to implement these projects.”

In the technical assistance realm, the discussions have been subdivided between headwater issues, dam/reservoir issues, and floodplain issues, recognizing that in a watershed approach, it often starts with one of those communities of practices, Mr. Mierzwa said.

Funding assistance

The funding assistance cornerstone is really about recognizing the value of inventorying all of the funding opportunities that are out there by pulling together these plans and documents, having a comprehensive story, and providing a gap analysis.  It’s also looking at the utilization analysis, which is determining how effective different projects are at actually reducing flood losses; in the emergency management world, that’s called a loss avoidance study.  After a federal declared disaster, agencies are by federal law required to document the effectiveness of the existing infrastructure and response structure so they can double down on what worked when making future investments.  “We’re talking about supporting that, and that also shows up within the water resilience portfolio.”

The partnership provides an opportunity to have floodplain-focused regional and local assistance program discussions so prior to the state starting a new program, they can get input from those who would be utilizing the programs as to what their biggest needs are now.  “We do that informally somewhat now but having a structure process through the partnership will only increase the effectiveness of that.”

Floodwaters from the Sacramento River overtopping the Tisdale Weir in 2019.
Photo by Florence Low / DWR


As for next steps, collecting data and gathering information will be a never ending effort.  “I like to say maps are kind of like milk; they have an expiration date, and unfortunately we have a lot of old maps here in the state of California,” said Mr. Mierzwa.  “We do make decisions on old maps, and those are not necessarily the appropriate decisions so we have an obligation to go through and update the maps and the data and information so we can make informed decisions.”

There is a need to conduct needs assessments for mitigation measures and their costs.  They’re considering building a resource portal where people could look at the existing resources that are out there that are less used, as well as providing technical assistance offerings.

A lot of local communities don’t realize they can call the Department and we can walk them through solutions and help them brainstorm,” he said.  “The idea is through the partnership, we might not be the only ones doing that.  They can talk to other local agencies, so we will facilitate those communications.  Then finally, identify and catalog the funding opportunities.”

There are over 2000 water management agencies in the state, many of them have flood management responsibilities, so they are hoping to bring more state and local agencies into the partnerships.


There are two pilot projects underway that DWR, FEMA, and CalOES are collaboratively working on.  The first is using existing bond funds for floodplain management for a pilot program to put gauges on some ungated spillways of dams across the state, focusing on those that have disadvantaged communities with some degree of hazard exposure downstream.  The issue is without a gauge on the spillway, there’s no way to know what the actual real-time flow rate coming from that dam or facility is, so they are looking to build some emergency alert notifications to downstream communities so that in the event of an uncontrolled spill from a dam, that the emergency responders downstream of that facility will be able to be aware of the degree of flooding that’s happening out there because an ungated spillway could flow a little bit or a lot, and the response will be predicated on the degree of flooding out there.

With the second project, DWR applied for a FEMA hazard mitigation grant after the 2018 Camp Fires to support post wildfire flood assessments where they are going into a few basins in Southern California, putting in additional gauges, and then building runoff forecasting tools and alert notifications for those watersheds.


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