The Brief

Researchers out of UC Irvine have said that nationally used flood modeling lacks specificity when it comes to measuring risks in urban areas like Los Angeles County.

They've created their own modeling system, PRIMo-Drain, that can better predict which properties are at risk when using accurate, granular data.

How the flood modeling system works

In a new report, UCI engineering professor Brett Sanders and his team compared widely used national flood risk assessment modeling in areas like Los Angeles County against their own PRIMo-Drain model. Long story short: Traditional models don’t usually include infrastructure like levees and dams, unresolved drainage and topographic data, which means their modeling is less specific when it comes to measuring risks for the spreading of floods in cities.

That data on storm drain infrastructures is collected mostly from GIS (geographic information system) shape files maintained by public agencies like the Los Angeles Department of Public Works. The UCI researchers also updated those databases with aerial image capture of the conditions of levees mapped in public records.

“Once we have this relatively detailed representation of the land surface, of the flood infrastructure, we look at different types of flooding,” Sanders said.

Those types of flooding include river floods, coastal floods, and flash floods from intense rainfall, like what Los Angeles saw the past two winters. Estimates show the frequency of extreme rainfall under a warmer atmosphere to likely be higher in seasons to come.

In recent years, large rainfall events in Southern California have been kept at bay by flood control infrastructure like those aforementioned levees and dams (the technical word for them is mainstem). But water is starting to reach above levee and dam walls more often. Places like Santa Barbara and San Diego experienced these flooding scenarios in the latest few rounds of atmospheric rivers.

This is why PRIMo-Drain researchers want to get as specific as possible in future models. If they could measure where water goes after escaping flood control walls and what areas get flooded, even more accurate models could be put to use for cities.

According to Sanders, part of this is why the developers of the model engage in “collaborative flood modeling” with the Los Angeles Regional Collaborative for Climate Action and Sustainability out of UCLA. The idea is to ask people where they see flooding, what they think drives flooding, and for suggestions on data sources that could help improve the model.

The model became publicly available in 2023. Since then, organizations like the City of Los Angeles and Southern California Edison have used PRIMo for planning and vulnerability measurement purposes.

Strategies to maintain flood risk

Right now Sanders and researchers on the PRIMo team are engaged in a two year study in Los Angeles in partnership with Los Angeles County and community groups to look at alternative strategies to manage this risk to communities and who they would benefit. (The same team also conducted a 2022 study that found L.A. County’s Black residents face disproportionately high flood risks.)

There are three strategies they’ve identified as potential solutions. The first is a tried and true method: make levees taller so that channels have more capacity and can prevent water from escaping the levee walls.

Another strategy involves widening channels to create more capacity, which would eliminate some of the concrete in channels and allow for vegetation to begin growing.

Sanders said the third strategy would be to “capture more storm water in the upper parts of the watershed…with more parks, more green space, and more infrastructure that would promote the infiltration of rainwater into the soil.” Ideally, this would reduce the amount of water that flows down these channels and in doing so reduce the risk facing these lowland cities.

In the meantime, the researchers will continue working on updating their models during future rain events. According to Sanders, it’s still “really hard to say [the researchers’] method is more accurate” since it hasn’t been exposed to enough severe flooding.

This story was originally published by Boyle Heights Beat on Nov. 25.

With the holiday season underway, organizations across Boyle Heights and East LA are seeking volunteers to help distribute food, assemble bicycles, sort toys and sponsor families in need.

If you’re looking to donate, volunteer or find ways to give back, we’ve rounded up a list to help you get started.

Build bicycles and organize donations at a toy giveaway

The Weingart East LA YMCA is hosting its 19th Annual Toy Giveaway on Dec. 18, and volunteers are needed to help prepare toys and provide support. Before the event, volunteers can help by assembling bicycles and sorting and organizing toys on Dec. 17 from 9 a.m. to 12 p.m. Volunteers are also needed to assist on event day from 3:30 p.m. to 8 p.m.

Volunteer at local food distributions

The Weingart East LA YMCA hosts a food distribution every Monday and Wednesday to ensure families have access to nutritious meals. Volunteers are needed for each food distribution from 8:45 a.m. to noon.

Drop off toys at First Street businesses

LAFC’s Expo Originals supporters group is collecting new, unwrapped toys and Venmo donations ahead of its annual community toy drive Dec. 14. Venmo contributions will go toward toy purchases, and the last day to donate is Dec. 6. Toys can be dropped off in person at the locations below until Dec. 13.

Donate a new jacket at a homeless shelter

Proyecto Pastoral is collecting new jackets to keep its participants at the Guadalupe Homeless Shelter warm.

Sponsor a family, child or classroom ahead of the holidays

Proyecto Pastoral has many opportunities for the community to give back during its Holiday Drive this year. Those interested in fulfilling holiday wishes for a family, child or classroom have until Dec. 1 to register. Proyecto Pastoral will pair sponsors with community members in need to fulfill items from their wish list.

Individual toys also can be dropped off at Proyecto Pastoral’s office. The toys will be distributed to children who participate in Proyecto Pastoral’s youth programs at their end-of-year celebrations.

Greystar, which manages hundreds of properties in California, has agreed to pay $7 million to settle a lawsuit alleging the company and other landlords used a price scheme to raise rents artificially high.

In January, Greystar was named as a defendant in an antitrust lawsuit filed by California Attorney General Rob Bonta, the U.S. Department of Justice and several other states against software company RealPage, which officials say uses algorithmic models to recommend price increases to subscribers.

Bonta alleges Greystar used RealPage’s system to coordinate rental prices with other landlords by illegally sharing and gathering confidential information. According to his office, RealPage’s “price alignment scheme” affected rentals across the country, especially in multifamily buildings in Southern California, including in Los Angeles, Orange County and San Bernardino.

"Whether it's through smoke-filled backroom deals or through an algorithm on your computer screen, colluding to drive up prices is illegal,” Bonta said in a statement. “Companies that intentionally fuel this unaffordability by raising prices to line their own pockets can be sure I will use the full force of my office to hold them accountable.”

Details on the settlement

Greystar is the largest landlord in the U.S., according to the Department of Justice, managing nearly 950,000 rental units across the country. In California, the company manages about 333 multifamily rental properties that use RealPage’s pricing software, according to Bonta’s office.

Bonta announced last week that as part of the settlement, Greystar has agreed to stop using software that uses competitively sensitive information to set rent prices, including from RealPage.

The company also has agreed to cooperate in the federal prosecution of RealPage and the other landlords named as defendants, such as Camden and Willow Bridge.

Greystar said in a statement to LAist that it’s “pleased this matter is resolved” and the company “remain[s] focused on serving our residents and clients.”

Settlement with RealPage

The U.S. Justice Department’s Antitrust Division filed a proposed settlement with RealPage on Monday to resolve its claims against the company.

If the settlement is approved by the court, RealPage would be required to stop using competitors’ private, sensitive information to set rental prices and remove or redesign features in its software that limited price drops or aligned prices between competitors, according to the Justice Department.

RealPage also would be required to cooperate in the lawsuit against property management companies that have used its software and agree to a court-appointed monitor to make sure it complies with the proposed settlement.

Dirk Wakeham, president and CEO of RealPage, said in a statement Monday that the proposed resolution marks an important milestone for the company and its customers.

"We are pleased to have reached this agreement with the DOJ, which brings the clarity and stability we have long sought and allows us to move forward with a continued focus on innovation and the shared goal of better outcomes for both housing providers and renters,” Wakeham said.

RealPage denies any wrongdoing, attorney Stephen Weissman said in a statement.

Newport Beach voters will decide if they want to replace a state-approved housing plan with one that allows for far fewer new homes in 2026.

Proponents of the plan, called the Responsible Housing Initiative, say the current plan will make the city overcrowded and negatively affect quality of life.

“This isn’t downtown Los Angeles,” said Charles Klobe, president of Still Protecting Our Newport, which backs the Responsible Housing Initiative.

Last week, city leaders voted to put the initiative in front of voters after the Newport Beach Stewardship Association submitted the Responsible Housing Initiative petition with more than 8,000 signatures. The initiative rejects the city’s current housing plan and instead proposes an amendment to the general plan to facilitate the development of 2,900 homes exclusively for extremely low-, very low-, low- and moderate-income households.

The city’s current housing plan, which has the backing of the state, allows for more than 8,000 homes, including the required affordable housing units.

“ We're against the city building more market rate than the state required. We believe it's a giveaway to developers who will fund re-election campaigns of the council,” Klobe said.

What does California law require?

California’s Housing Element Law sets housing targets for local governments to meet, including for affordable units. It allows the state to intervene every eight years to let cities know how much housing they must plan for. The law also requires cities to put together a housing element showcasing how they will achieve the state’s plan. The state then approves of the element or sends it back to cities to reconfigure according to the requirements.

According to California law, Newport Beach needs to build 4,845 new units — 3,436 of which must be affordable for very low-, low- and moderate-income households. According to the city, Newport Beach can’t just plan for affordable housing units “because that would assume all future projects would be 100% affordable, which is not realistic based on previous development experiences.” And so, the city’s rezone plans include more than 8,000 units.

Councilmember Robyn Grant said during the council meeting that she’s not in favor of the state mandate. But, she added, “After extensive legal analysis and public outreach and workshops and hearings and meetings and more meetings, this council approved an updated general plan to bring Newport Beach into compliance and avoid serious penalties, including the loss of local land use control."

Newport Beach did appeal the state’s housing mandates on the grounds that it did not take into account how some of the city’s coastal lands are protected from urban development, but the appeal was rejected.

To learn more about how Newport Beach arrived at its state-approved housing plan, click here.

What is the Responsible Housing Initiative proposing?

The Responsible Housing Initiative counts the number of housing units already in development and proposes an additional 2,900 affordable housing units to meet the state mandate.

Klobe said they believe the initiative will receive state backing because “they claim to want affordable housing and our initiative requires it.”

Supporters of the measure contend the city’s current plan will increase the population, result in excessive traffic and disrupt the quality of life. They also sued Newport Beach for not first going to voters, but they failed in court.

To learn more about the Responsible Housing Initiative, click here.

What’s next

Voters will have a chance to weigh in on the Responsible Housing Initiative in November 2026.