After the Park Fire began in Bidwell Park on July 24, 2024, burned ground sheds rain faster and carries more sediment. A Butte County technical memo dated November 25, 2024 estimated post-fire flows at the Five-Mile diversion. Those estimates describe the system, not every lot, so a homeowner should read the house itself.
Key takeaways
- The Park Fire began in Bidwell Park on July 24, 2024.
- A Butte County technical memo dated November 25, 2024 estimated the diversion overtops at about 1,950 cubic feet per second under pre-fire conditions.
- The same memo estimated post-fire flows of about 10,510 cubic feet per second for a 2-year storm and about 18,810 for a 10-year storm.
- Those figures describe the Five-Mile diversion as a system. They do not show which Chico lot or house takes water.
- Burned ground sheds rain faster and carries more silt, so the same storm can behave differently after a fire.
- A homeowner's best protection is to know where water enters the house and to keep records of any water that does.
What happened when the Park Fire began?
The Park Fire began in Bidwell Park on July 24, 2024. A fire changes the ground it burns, and that change matters for storm water long after the flames are out.
Vegetation and the layer of organic litter under it normally slow rain and let it soak into the soil. A fire removes that cover and can change the soil surface, so rain runs off faster and carries more loose material with it. The effect is strongest in the first storms after a burn, and it can continue for some time as the ground settles.
The fire began in Bidwell Park, which is part of the same landscape that feeds the creek system around Chico. That is why the County and the City have looked at how storm water from the burned area would reach the city and its drainage.
What did the County's November 2024 memo estimate?
A Butte County technical memo dated November 25, 2024 estimated the Five-Mile diversion overtops at about 1,950 cubic feet per second under pre-fire conditions. It estimated post-fire flows of about 10,510 cubic feet per second for a 2-year storm and about 18,810 for a 10-year storm.
The estimates describe the flow the system might carry, measured in cubic feet per second, for storms of different return periods. A 2-year storm is one with a fairly regular chance of occurring in any year, and a 10-year storm is rarer. The numbers show how far the post-fire flows could exceed the pre-fire overtopping figure.
The estimates are for the system at the city. They are useful for planning, and they show why a homeowner should take the burn seriously. They do not identify which street or house will take water, and a reader should not treat them as a flood map.
A burn also changes the ground over a longer period. Vegetation returns slowly, and the soil can take time to settle into a new surface. A homeowner who reads the County's figures in the first year after a fire may want to revisit them as the landscape changes, rather than treating one memo as the final word on the risk.
The memo is a technical document, so its tables and assumptions are worth reading in full if you have the chance. A short summary cannot carry every condition behind its figures, and the County's own wording is the reliable version.
How does the flow estimate become a risk at a house?
A flow estimate becomes a risk at a house only where water can reach the house, through grade, drainage, openings and the level of the lot. The estimate sets the scale; the property decides the route.
Water reaches a house by way of its lot. A lot that drains away from the house takes water away, and a lot that drains toward the foundation can take it in. Openings at grade, such as vents, window wells and door sills, are where water enters if it is high enough to reach them.
So the honest question for a homeowner is not whether the diversion will overtop, but whether water can reach their own lot and enter their own house. That question is answered by walking the lot, reading the grade and noting where water has gone in past storms.
What does sediment add to the picture?
Sediment is the fine material that water carries and leaves behind. After a burn it can be heavier, and it holds moisture against materials after the surface has dried. Sediment also builds up in the Five-Mile Basin during high water.
A 2021 state notice limited the County's periodic removal of deposits from the basin. A basin with more deposit in it has less room for water, and that changes how the system responds to a high flow. The County's technical work is the place to read the detail.
For a homeowner, sediment means cleaning and drying take longer than they do after clean water. Silt that settles on a floor or in a crawl space must be removed before drying can reach the material beneath it.
What can a homeowner check now, before the next storm?
Walk the lot after a storm, note where water runs and where it pools, check the openings at grade, and keep the gutters and window wells clear. Keep a short written log of each storm and any water that enters.
Walk the lot with the rain running, if it is safe. Watch where the water goes, which way the grade falls and whether any opening at the foundation takes it. Take photographs of the path and any pooling.
Clear the gutters, downspouts and window wells before the rains. Make sure the downspouts carry water away from the foundation. Keep a note of each storm, the water you saw and where it entered, since that record helps you and any crew that is called.
What should I do if water comes in after a storm?
Keep people and pets out of standing water, turn off power to wet areas if you can do it safely, photograph the water and silt, and call for extraction. Keep the damaged materials until your insurer has seen them.
Calls for water extraction are answered 24/7 at (833) 490-5225, and a crew is sent as fast as one is available. No arrival time is promised. The crew reads the water and the silt, which tells it how the water arrived.
Keep a written record of the storm, the time you first saw water and every step you took. The insurer will review that record, and the crew uses it to explain what it found.
Where can a homeowner read more about the planning picture?
The City of Chico's General Plan update covers the drainage system in its draft environmental impact report, under section 4.9 on hydrology and water quality. The County's technical memo is the source of the flow estimates quoted here.
The General Plan update is published by the City of Chico, and its draft environmental impact report contains a section on hydrology and water quality that covers the same drainage system. A homeowner who wants the planning context can read that section on the City's website.
The County's technical memo of November 25, 2024 contains the flow estimates quoted in this guide. It is a planning document, and it is best read alongside the City's report rather than in place of it. A restoration crew can explain what it found in your house, but it does not interpret the planning documents for the County or the City.
How should a non-specialist read these flow figures?
Read the figures as the scale of a planning problem, not as a prediction for one address. The memo's numbers are for the system, and the useful question for a household is what the water does on its own lot.
Cubic feet per second is a rate. A larger number means more water passes each second, and the memo compares the diversion's pre-fire overtopping point with the larger flows estimated after the fire. The comparison is the important part, because it shows how much more water the system might have to handle.
A household does not need to model the flow. It needs to know whether water can reach its own lot, and that is answered by the grade, the drains and the openings. A simple walk of the property in a storm, with notes and photographs, is more useful to a homeowner than any single flow figure.
Keep your own notes alongside the County and City documents. A note that says where water stood after a particular storm, with the date and a photograph, is the kind of local observation that stays useful long after the memo has been filed and forgotten.
Frequently asked questions
Does the County memo mean my Chico house will flood?
No. The estimates describe the Five-Mile diversion as a system. Whether water reaches your house depends on your lot, its grade and its openings.
What does cubic feet per second mean?
It is a measure of how much water passes a point each second. The memo uses it to describe the flow the diversion can carry and the larger flows it may have to carry after a fire.
Is the burn area still changing the runoff?
The effect of a burn on runoff is strongest in the first storms, and it can continue as the ground settles. The memo's estimates are planning figures, and they do not say how long each effect lasts.
What should I photograph before the next storm?
Photograph the lot, the grade, the openings at the foundation and the drains, so you have a baseline. Photograph them again after a storm to see what changed.
Who should I call if water comes in?
Call your insurer to report the loss and a restoration crew for extraction and drying. The crew reads the water and records its path.
Should I buy flood protection because of the memo?
That is a decision for you and your insurer. The memo does not identify your property, so the most useful step is to understand your own lot and talk to your insurer about the coverage that applies to it.
Will the risk stay the same over time?
The memo describes conditions at the time of its estimates, and the ground can change as the burn area recovers. Treat the figures as a planning baseline, and watch your own property over the coming seasons.
Sources
This guide is general information for Butte County homeowners, not a substitute for an on-site inspection. Prices are estimates. See our disclaimer.