04-21-2023, 03:45 PM
I have a son that lives just off the NE corner of the new delta and watching the water levels this spring left me asking how will the area handle this year's high runoff. I pinged the USBR and asked them.
Their response seemed reassuring and well thought out.
I especially liked their anticipated view that says we could get another 3' rise in lake level by/during the peak runoff.
We are already 3' higher than last fall's low point and equal to the last summer's highest level. If we get 3 feet or more added this season, we will get almost to the full (compromise) level for the first time since April of 2020!
From the images at the bottom: A) is where we are now, B) is their anticipated peak based on the 10 year high flow and C) is what it will look like in a normal summer after the runoff is over.
Here is their response:
"Hi again Jim,
Things have been kind of crazy around here, so sorry for the delay - I've got some info for you in response to your questions about high flows in and around the delta this spring:
Here’s what we’re focusing on to manage high flows in different areas:
As you gathered from our flier, we do not plan to release high flows down the old river channel. The Delta was designed to receive all the river’s high flows and to restore the ecological benefits of natural overbank flooding. Releasing high flows down the old channel would damage the diversion and small downstream dam.
This figure illustrates how the Delta is designed to flow out of bank at high flows. As of mid-April, river and lake conditions are similar to scenario A. Conditions similar to scenario B are anticipated later this spring.
Hope this info addresses your concerns. Please let me know if you have further questions!
Thanks,
Diane"
Their response seemed reassuring and well thought out.
I especially liked their anticipated view that says we could get another 3' rise in lake level by/during the peak runoff.
We are already 3' higher than last fall's low point and equal to the last summer's highest level. If we get 3 feet or more added this season, we will get almost to the full (compromise) level for the first time since April of 2020!
From the images at the bottom: A) is where we are now, B) is their anticipated peak based on the 10 year high flow and C) is what it will look like in a normal summer after the runoff is over.
Here is their response:
"Hi again Jim,
Things have been kind of crazy around here, so sorry for the delay - I've got some info for you in response to your questions about high flows in and around the delta this spring:
Here’s what we’re focusing on to manage high flows in different areas:
- At the diversion structure and small downstream dam (which will remain in construction mode for many more months): we are working to shore up protections to be ready for high river flows and rising lake levels.
- Around the Delta perimeter: we have accelerated the schedule for building up the berms around the Delta perimeter to protect surrounding properties from river-caused flooding. This includes work on the southern delta boundary berm.
- New channel upstream of Lakeview Parkway and near Lakeview Parkway bridge: we have accelerated the schedule for building up berms on both sides of the new channel upstream of Lakeview Parkway. Crews are on alert and staging equipment in case flood debris creates problematic obstructions near Lakeview Parkway bridge.
- In the Delta: “flood preparation” is built into the design of the delta itself in the form of a natural, connected floodplain. The channels and ponds are meant to overtop and spread out during high flow periods, dissipating flood energy (see the figure below). This is in contrast to rivers confined between narrow levees, where conditions can only get faster and deeper during floods. Overbank flooding is an important ecological process that deposits nutrient-rich sediment, creates habitat, and jump-starts the growth of native riparian plants like cottonwoods.
As you gathered from our flier, we do not plan to release high flows down the old river channel. The Delta was designed to receive all the river’s high flows and to restore the ecological benefits of natural overbank flooding. Releasing high flows down the old channel would damage the diversion and small downstream dam.
This figure illustrates how the Delta is designed to flow out of bank at high flows. As of mid-April, river and lake conditions are similar to scenario A. Conditions similar to scenario B are anticipated later this spring.
Hope this info addresses your concerns. Please let me know if you have further questions!
Thanks,
Diane"