Sacremento-San Joaquin Delta

In January 1997, California faced one of the largest and costliest floods in the state's history. Due to the annual return of El Niño, heavy rainfall during this period was not unique. But what was different from normal years was that a La Niña occurred this year. With La Niña, sea water temperatures in the Pacific are lower than average. Passat winds cause more cold water to come to the surface from deep (Philander, 1985).

The severity, duration and amount of rainfall of the storms were greatly underestimated and as a result California was not prepared for the consequences. The heavy rains caused the water reservoirs to fill up. Because these were full, they were automatically emptied into the already overflowing rivers. As a result, the rivers overflowed and many of the levees in California broke. (O'Brien & Payne, 1997). Over thirty levees broke and over 144,840 km2 of land flooded (Independent Review Panel, 2007). The video on the right shows an example of what the delta basin would look like if the levees broke. In the movie, the levees break because of an earthquake. The probability of earthquakes is very high in California (Gutenberg & Richter, 1944).

During the 1997 floods, 23,800 homes were destroyed, nine people were killed, and there was total damage of $2 billion (Schmidt Sudman, 1997). An estimate from a report by Burton and Cutter estimated the total population in 2019 that would live in this area behind the levees to be over one million people (2008). Therefore, it is of global importance that the levees do not breach again.

A study by Medellín-Azuara et al. analyzes the effects of increasing salt in the soil (2014). This gets into the soil after there has been a flood and the salt water has free rein to flow inland. Due to the salty soil, crops cannot grow properly and farmers lose their income. Another reason salinity is increasing is sea level rise. Much of the delta is sea level and as sea levels continue to rise, the likelihood of dike breaches will increase.

But are the levees in this area really being strengthened? Scientists regularly point out the weaknesses of levees in the Sacramento-San Joaquin Delta. But policymakers don't need to know about them and say there are too few grants for them (Lund, 2011).