[M T]

....Similarly, no one is proposing that we construct a dam in Pasadena to capture rainwater runoff from the San Gabriel mountains.

Between the Hurst Fire (Sylmar) and the Eaton Fire (Altadena), just south of and very visible from I-210, is the Hansen Dam, that was built to protect the L.A. River from flooding.  When it was completed in 1940, it was the largest in the world of its type.  It does not have a reservoir, but it apparently still functions to avoid flooding of the L.A. River (if you can call a concrete channel a river). You can read about this and some other LA County dams.  The article also covers another dam that was in Sylmar.

If you want to follow up on the soffit vents or other aspects of homes in wildfire zones, FEMA published a set of Fact Sheets in 2008.

AFAIK, California's general water supply situation had nothing to do with the fires, but as for the comment above about new dams, it seems the poster knew ("as of this writing") that construction on a new California reservoir is due to start in 2026. As for why it takes so long from an idea to construction, see my link above on the L.A. County dams.

[M T]

....Similarly, no one is proposing that we construct a dam in Pasadena to capture rainwater runoff from the San Gabriel mountains.

Between the Hurst Fire (Sylmar) and the Eaton Fire (Altadena), just south of and very visible from I-210, is the Hansen Dam, that was built to protect the L.A. River from flooding.  When it was completed in 1940, it was the largest in the world of its type.  It does not have a reservoir, but it apparently still functions to avoid flooding of the L.A. River (if you can call a concrete channel a river). You can read about this and some other LA County dams.  The article also covers another dam that was in Sylmar.

If you want to follow up on the soffit vents or other aspects of homes in wildfire zones, FEMA published a set of Fact Sheets in 2008.

AFAIK, California's general water supply situation had nothing to do with the fires, but as for the comment above about new dams, it seems the poster knew ("as of this writing") that construction on a new California reservoir is due to start in 2026. As for why it takes so long from an idea to construction, see my link above on the L.A. County dams.