by Jay Lund

The tweet below, shows slight (but still frightening) levee overtopping this week on Cache Creek, just north of Woodland, California.  It also illustrates the combined operations of flood preparation and response, with a simultaneous floodplain evacuation order.  Integrating a range of preparations and responses have made the Sacramento Valley much safer from floods.

One often hears, “If only we did X, we would solve this problem.”  Alas, effective solutions are rarely so simple or reliable.  Most robust solutions for problems involve a diverse and complementary portfolio of actions, developed over time.  When a set of diverse actions are carefully crafted to work together, they often provide more effective, adaptable, and reliable performance, at less expense that a single solution.

The Sacramento Valley’s flood management system is a good example where a portfolio of actions has greatly reduced flood damages and deaths, with relatively little management expense and attention in a highly flood-prone region.  This case also illustrates how the many individual flood management options presented in the table can be assembled into a diversified cost-effective strategy involving the many local, state, and federal parties concerned with floods.

Portfolio strategies usually include actions which work in different ways over different times.  Flood management portfolios usually include actions that prevent flooding (such as levees) complemented by actions that reduce the need for more expensive flood prevention (such as flood evacuations).  Actions which protect areas from flood waters (often structural actions) are distinguished from actions that reduce vulnerability to damage and death if flooding occurs.  Levees, bypasses, and reservoirs are all designed and operated to support each other in the Sacramento Valley to reduce the extent of flooding.  Floodplain land management and flood warnings and evacuations have greatly reduced the property and people exposed to flooding.

Because most floods occur and pass quickly, most flood management is in preparing for floods and flood recovery, rather than in response during actual floods.  As with fire-fighting, elections, and war, flood management time is more than 99% preparation and recovery and less than 1% actions during flood events.  Pre-flood preparations to contain floods (with levees, reservoirs, and bypasses), reduce flood damage potential (with evacuations, building codes, insurance, and floodplain zoning), and prepare for rapid flood operations and evacuations (with education, warnings, and training) are crucial.  Making and coordinating investments, training, and education are all prominent before floods, making urgent flood operations more effective (and less panicked).  Post-flood response also can reduce flood damages and help prepare for the next flood.  There is always a next flood.

Portfolio solutions require overcoming some challenges, however.  Because portfolio solutions involve a range of actions usually controlled by different authorities and groups, they require more social and political organization than single-action silver-bullet solutions.  This can take time, motivation, and leadership to bring together.  But such diversification of responsibility for implementing portfolio can help spread expenses and provide useful perspectives of attention to details and effectiveness.  In flood management, local residents and land owners, local governments, regional governments, and state and federal agencies all specialize in different elements of regional flood management.  This specialization helps lower costs, increase attention to detail, and diversify political support.  This can lead to a mutually-reinforcing ecosystem of institutions that are collectively more effective at attending the problem and innovating than would a single larger bureaucracy.

It took decades for California’s Sacramento Valley to build its current flood management portfolio.  Even so, some flood problems remain.  Small towns and some rural industries remain vulnerable – and there is always vulnerability to bigger floods and infrastructure failures.  There will always be residual flood risks, as flood solutions are never perfect or complete.

Flood problems also change as the economy, population, social expectations, and now climate change.  We now see floodplains and flood bypasses are closely linked to California’s environmental solutions, bringing new objectives in our flood discussions. Portfolio solutions can often better incrementally adapt to change because of their supporting diversified institutional network and operational flexibility.

Successes with water problems (and other areas) often comes from developing or evolving portfolio solutions.  An integrated range of institutions supports this management, mixing the advantages of centralized and decentralized governance and finance to make more effective and adaptable solutions at less expense.  No single person or institution can usually solve such problems.

A series of blog post essays will explore the use and development of portfolio solutions for major water problems.  Successes and challenges will be discussed, as well as the problem of coordinating portfolios of actions across problems – such as managing a common water infrastructure for floods, water supply, and ecosystems – which traditionally have separate solution portfolios.

Further Reading

California Department of Water Resources, Central Valley Flood Protection Plan, https://water.ca.gov/Programs/Flood-Management/Flood-Planning-and-Studies/Central-Valley-Flood-Protection-Plan

Gilbert F. White (1937), Notes on Flood Protection and Land-Use Planning, Journal of the American Institute of Planners, 3:3, 57-61, DOI: 10.1080/01944363708978728

Independent Forensic Team (2018). “Independent Forensic Team Report: Oroville Dam Spillway Incident”. January 5, (2018).

Jeffres, C.A.; Opperman, J.J.; Moyle, P.B. (2008), Ephemeral floodplain habitats provide best growth conditions for juvenile Chinook salmon in a California river. Environ. Biol. Fishes, 83, 449–458.

Kelley, R. (1989), Battling the Inland Sea; University of California Press: Berkeley, CA, USA.

Lund, J.R. (2012), “Flood Management in California,” Water, Vol. 4, pp. 157-169; doi:10.3390/w4010157.

Jay Lund is a Professor of Civil and Environmental Engineering at the University of California, Davis.