Alameda County staff to keep using current USGS watercourse maps until USGS rolls out 3D hydrography; residents urge reinstating 2015 maps

Alameda County Public Works staff recommended the county continue to rely on the current USGS map in the Watercourse Protection Ordinance (WPO) and defer substantive ordinance changes until USGS issues its new 3D hydrography products, which staff said are expected in mid‑fiscal 2025.

Daniel Wildesenbeth, who the meeting identified as the presentation lead, told the Transportation Planning Committee "The Watercourse Ordinance will continue to rely on the most recent USGS map for the watercourse designation," and said USGS is moving to a lidar‑based program that assigns a stream 'periodicity' or 'stream permanence' value rather than the older ephemeral/intermittent/perennial labels.

Why the county is waiting: Wildesenbeth said the 3D Hydrography Program (3D HP) will add elevation and flow‑period metrics that are longitudinal over time, allowing the county to translate USGS 'periodicity' values into local regulatory categories. He told supervisors his recommendation is to "continue to use the current USGS map as stated in the ordinance" and to revisit the WPO after USGS publishes its new mapping so the county can adopt measurable thresholds for which channels it will regulate.

Residents and watershed groups pushed a different course. Public commenters described local flooding and habitat loss, presented ground‑truthing data and urged the county to restore the 2015 USGS topo maps to the WPO now. Chuck Meadows, who said he lives adjacent to an affected creek, said he has incurred large personal expenses because of nearby development and noted, "According to the map that I printed this morning, I now have a river behind my house." Bruce King of Friends of San Lorenzo Creek described a 74‑page study and said the group’s ground truthing of 58 streams showed flows meeting USGS and state definitions of intermittent streams; he urged immediate readoption of the 2015 maps.

Environmental advocates pressed the county to act sooner. Matt Turner, speaking for the Sierra Club, said "The claim that the 2018 mapping change is a correction of historical errors is simply false" and argued the county’s reliance on the newer USGS products has "resulted in the significant diminishment of Alameda County's ability to understand and protect its watersheds." Other speakers cited recent flooding on Kelly Creek and potential downstream impacts if small, intermittent channels are left unprotected.

Legal and practical limits: Deputy County Counsel Kathy Lee told the committee that private remedies for property damage remain available and that the WPO definition primarily governs county enforcement jurisdiction, saying there "are remedies for property damage, in between private citizens" but that those are distinct from county enforcement authority under the ordinance.

Next steps: Supervisors asked staff to gather examples of how other Bay Area counties and cities treat mapping and to invite USGS and Fish & Wildlife representatives to appear before the committee. Staff said it can forward citizen submissions to USGS for their evaluation but does not currently have capacity to independently vet every submission; the committee asked staff to review the 58 creeks submitted by Friends of San Lorenzo Creek and tentatively requested a follow‑up briefing by August 5 to report findings and to attempt to schedule USGS and Fish & Wildlife presentations.

The matter was presented as an informational update; no formal action or vote was taken at the committee meeting.