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Integrating Future Data

The data-based methodology of the Master Plan is specifically designed to be updated as new data becomes available in coming years.

The standardized river ruler format allows new data to be easily compared with other data in river projects.

This adaptable methodology will allow the Master Plan to be valuable even as new research on climate change, LA County assets, and ecosystems becomes available in coming decades. The Master Plan goals, actions, and methods outline studies that should be undertaken, including asset mapping for arts and culture, ecosystem, updated hydrology modeling, continued climate change research. Also, studies currently underway, such as the LA River Environmental Flows Study, will provide additional data in coming years.

The ability to integrate future data allows the master plan to become stronger as new data becomes available

As quantitative and scientific datasets become more robust, this data should not negate LA River residents’ lived experiences of displacement, pollution, racism, and other injustices. Even within large datasets there can be gaps of information. Qualitative narratives from LA River-adjacent communities will continue to be needed to contribute to filling these gaps of information.


Data for ecosystems in LA County and along the LA River range in scale, extent, resolution, and time of study, but compiled together paint a picture of the region’s unique biodiversity and the role the LA River can play in enhancing urban ecology. While some portions of the river have been studied in great detail, future data produced through a more comprehensive and consistent analysis of species diversity and habitat conditions along the full 51 miles of the river would provide a more detailed and updated picture of the river corridor’s habitat areas than existing CALVEG landcover vegetation data. As data on existing habitats improves, tools and policies like the City of LA’s Biodiversity Index and ecotype classifications can help further guide the effective management of the region’s urban biodiversity. In addition to new data mapping and classifying habitat areas at finer resolution, critical linkages for habitat connectivity may also change as habitat areas expand and as new studies such as the National Parks Service’s LA River Wildlife Camera Project reveal how wildlife use the LA River corridor for habitat and connectivity. Additionally, as the State Water Resources Control Board and the Regional Water Quality Control Board’s LA River Environmental Flows Study advances, and dry season instream flow requirements are established, this data can feed back into the Master Plan database allowing project proponents to better understand available instream flows for project design.

In addition to current ecological system data, researchers at the University of Southern California and the University of California Los Angeles are developing a historical ecology database, preliminarily referred to as HELAR (Historical Ecology of the LA River).1For more information see Los Angeles Landscape History.

Climate Change

While climate change is projected to increase extreme heat events in the LA Region, there is greater uncertainty around how future climate conditions may increase or decrease the region’s annual precipitation. However, it is generally accepted that warmer temperatures will result in more moisture in the air and lead to more intense storms. Some climate change projections indicate a “threefold increase in sub-seasonal (extreme precipitation) events comparable to California’s Great Flood of 1862” by 2100.2Daniel L. Swain, Baird Langenbrunner, J. David Neelin, and Alex Hall, A. Increasing precipitation volatility in twenty-first century California. Nature Climate Change 8, pages 427–433 (2018). Other research indicates under certain emission scenarios that the 1% storm event (i.e., 100-year storm) 24-hour rainfall total in LA may increase by approximately 20%, and the 1% storm event of today will become the 1.5% (i.e., 67-year storm) event in the future.3Daniel L. Swain, Baird Langenbrunner, J. David Neelin, and Alex Hall, A. Increasing precipitation volatility in twenty-first century California. Nature Climate Change 8, pages 427–433 (2018).

Projected future return periods for a current 1% (100-year) storm event for Representative Concentration Pathway (RCP) 4.5 (“Stabilization”) and RCP8.5 (“Business-as-usual”) scenarios across California. Most locations indicate that the current 1% (100-year) storm event will become more frequent (i.e., shorter return periods).
Modified from AghaKouchak, Amir, Elisa Ragno, Charlotte Love, and Hamed Moftakhari. (University of California, Irvine). 2018. Projected changes in California’s precipitation intensity-duration-frequency curves. California’s Fourth Climate Change Assessment, California Energy Commission. Publication Number: CCCA4-CEC-2018-005.

As research continues, new and improved climate projections should be used to update the Master Plan. In addition to climate change research being led by LA County Public Works in coordination with academic institutions, the LA County Sustainability Plan, “Our County,” will be working to develop vulnerability data for LA County. The work of the LA River Master Plan and the Sustainability Plan should continue to be coordinated as both plans are implemented.

Global Models

Agencies around the world contribute to climate change modeling. For example, since 1995, the World Climate Research Programme’s (WCRP) Coupled Model Intercomparison Project (CMIP) has utilized a set of widely referenced collaborative climate models to anticipate climate change under assumed different greenhouse gas emission scenarios. The CMIP4World Climate Research Programme, “WCRP Coupled Model Intercomparison Project (CMIP).” has undergone several iterations and is now on its sixth phase. Accuracy increases as each iteration draws on new technological and computational advances.

Local Effects

Results of global climate change models must be downscaled to adequately address localized effects. In Southern California, diverse topography and small-scale climate variations can make storm conditions difficult to capture accurately in global climate models.5D.L. Swain, B. Langenbrunner, J.D. Neelin et al,. “Increasing precipitation volatility in twenty-first-century California,” Nature Clim Change 8 (2018), 427–433. Additionally, it is important to develop an understanding of certain phenomena, like atmospheric rivers, that have been responsible for many extreme historical flooding events in California. These long bands of water vapor originating over the Pacific Ocean are predicted to increase in strength as warming continues. Increased temperatures are known to lead to increased moisture retention and ultimately to increased rainfall intensity.

Updated Hydrology Modeling

A key factor in managing flood risk along the LA River is having an accurate understanding of the hydrology. The hydrology of the LA River statistically evaluates how much rainfall runoff from various sized storm events (i.e., 50% through 0.2% storm events) will flow into and along the LA River. The Master Plan is based on the best available hydrologic study of the entire LA River watershed, much of which was developed nearly 30 years ago by the US Army Corps of Engineers.6USACE Los Angeles District. 1991. Los Angeles County Drainage Area (LACDA): Review, Part I Hydrology Technical Report: Base Conditions.

It is imperative that the hydrology be updated so that project investment decisions are informed by the most recent flood frequency information

Since then, there are 30 years of additional rainfall data to base statistical hydrologic analyses on, in addition to improved modeling capabilities. With the strategic directions in mind, to advance projects that meet the Master Plan goals, it is imperative that the hydrology be updated in the near future so that project investment decisions are informed by and incorporate the most recent flood frequency information.

Comparison between current and projected rainfall intensity for the 1% (100 year) precipitation event. For example, the 1-day (24-hour) storm total may increase from 7 to almost 8 inches indicating larger storm events are more likely in the future.
Modified from AghaKouchak, Amir, elisa ragno, Charlotte Love, and Hamed Moftakhari. (university of California, Irvine). 2018. Projected changes in California’s precipitation intensity-duration-frequency curves. California’s Fourth Climate Change Assessment, California energy Commission. Publication number: CCCA4-CeC-2018-005.

Arts and Culture Assets

The existing datasets for arts and culture include features such as major art institutions and standard community facilities, but are far from capturing the full breadth of community assets the LA River has to offer and the rich cultural heritage of the LA River. In order to realize a 51-mile arts and culture corridor for the LA River and to understand where gaps in these assets are, a methodology should be developed for the inclusive mapping of arts and culture in neighborhoods adjacent to the river. This methodology should be participatory and include informal and improvisational community spaces and groups, as well as temporary art installations and recurring community events and festivals. Mapped assets should also include places, people, and events that convey the cultural heritage of riverside communities. An example of comprehensive field mapping is the City of LA Department of Planning’s SurveyLA Program, which was completed from 2010 to 2017 and identified historic resources for each community plan area of the city.7Historic Resources Survey. Los Angeles City Planning. Accessed March 24, 2020.

The LA County Department of Arts and Culture, along with LA River artists and arts organizations, local Indigenous Peoples culture bearers, and other community partners, will be undertaking the creation of the mapping methodology and the reporting of the asset data itself. Given the dynamic nature of arts and culture, this mapping would ideally live in an online platform and include self-reported vetted data that would capture the most current state of community assets. When executed, this more thorough data on arts and culture could be used to update the Master Plan, better identify neighborhoods along the LA River with the greatest need for arts and culture spaces and programming, and ensure social and cultural preservation of sites and stories of historical significance. As development and construction takes place along the river, cultural historic resources need to be safeguarded. Mapping these sites is an important way to ensure the historic and social fabric is not lost or if it is threatened, mitigation is provided.

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