I live in Sacramento, there is some context the author may not have been aware of.
First off, hydrology and specifically excess water management in the valley is often geared toward irrigation and replenishing ground water. We have areas that are suppose to become flooded to keep the pressure off of the earthen levees along the river and delta (created by the confluence of the Sacramento to and San Joaquin rivers) as the water drains into the San Francisco Bay. This gives us a way to slow the discharge of water give it time to soak in join the water table. There are improvements here like widening the river channels we’ve carved out to expose more surface area for it to soak into, but there are no plans for this afaik.
Second, we have a network of creeks, canals, and drainage ditches that move excess water to less harmful places, Dry
Creek (which is dry most of the year) was carrying water as it should in march. These provide essential, perennial habitats that were once naturally occurring, and are filled and let dry by design.
Like most new media coverage, with this article being no exception, there is a tendency to focus on the main dams, but in the case of the American River, there are 5 dams in all managing water flow, with a dozen or so more impounding various tributaries. Combined this is known as the Upper American River Project, which acts a extra power capacity that SMUD (Sacramento’s community-owned power company) can turn on quickly. This network holds back nearly 430,000 acre/ft of water. A cascading failure in these dams can cause a significant portion of this (with the total capacity being released as almost 1/2 of Folsom’s capacity) could cause a spillway event and a wall of water careening downstream and potentially rupturing levees that were not rated for this volume. Because of the nature of the river’s bend and the narrowing of distance between the banks, the most obvious spot a break would occur is near Sacramento State University and would fill up the River Park neighborhood instantly given that exists between two levees when a new one was built to restrict the flow of the river so they can build more homes. The floodwaters would make it to downtown, destroying the affluent area of East Sacramento, Midtown, and running south through land park, elmhurst, and oak park. This is just one disaster scenarios that could lead to post-Katrina New Orleans type of flooding, with only hours of warning to execute a poorly planned evacuation.
The upper American River project series of damns is fairly well maintained, but for every Sierra Nevada snowmelt River that drain into then Sacramento or San Joaquin, there is a similar network of dams at varying levels of repair, waiting for a large cascading failure event to give the poor unsuspecting towns in the valley an unfortunate surprise.