Field Journal: 26 February 2019 - Flooded Forest Special Edition

We got swamped. Heavy rains from a strong atmospheric river system flooded in the valleys here in Marin County, and the alluvial flat at Roy's Redwoods was no exception. On Tuesday of this week, I donned head-to-toe rain gear, bundled my photography gear into water-resistant bags, and headed into the forest to capture video of the resulting streamflow.

Flooding in the alluvial flat at Roy's Redwoods on 26 February 2019

As you can see in the photo above, the floor was made of water. I tested the limits of my rubber boots on this hike, and some streams were too deep to cross. A big umbrella provided cover while I shot photos and video.

Streamflow in the creek near the Nicasio Valley Road trailhead on 26 February 2019

The seasonal creek running parallel to Nicasio Valley Road drains most of the preserve. Roy's Redwoods can't be accessed without crossing this creek. A bridge normally provides access to the southern part of Roy's Redwoods Loop Trail, but the path from the trailhead to the bridge is covered by water too deep to cross without knee-high boots.

Streamflow in the creek near the Nicasio Valley Road trailhead on 26 February 2019

This is the same creek as above, looking downstream toward the bridge. To reach Meadow Trail and the northern part of Roy's Redwoods Loop Trail, visitors must wade this creek at a shallow crossing upstream of the bridge.

Flooding on Meadow Trail near the Nicasio Valley Road trailhead on 26 February 2019

Heavy rain turns trails into shallow streams.

Spillover from a flooded creek along Meadow Trail in the alluvial flat on 26 February 2019

The area shown above receives a lot of foot traffic. It's along Meadow Trail near the trailhead, and the Coast Redwood ring there gets a lot of attention from visitors. Heavy foot traffic results in hard-packed soil, which can't absorb as much water as loose soil. This water drains into the area shown above.

Streamflow in the alluvial flat on 26 February 2019

Water flows deeper and more vigorously in the natural stream beds.

Spillover from a flooded creek along Meadow Trail in the alluvial flat on 26 February 2019

This is another area that gets a lot of foot traffic. You can see how the spillover from the flooded creek on the left has spread across the hard-packed soil on the right.

Flooded creek in the alluvial flat on 26 February 2019

This is a swollen creek further south in the alluvial flat. Extensive pooling in the background is a result of an obstruction in the creek bed: a large amount of debris has accumulated at a point where the creek flows around a fallen redwood.

Flooding in the alluvial flat on 26 February 2019

This is further downstream from the previous video. The area shown above isn't normally a stream bed. This is where spillover from the debris-choked creek has formed a new pathway. It's the same place I photographed erosion around redwood roots last week.

Same area as above, last year

Finding this older photo of the same area was a little bittersweet. Much of the soil has been carried away in the flood, leaving redwood roots exposed at a depth of up to 6 inches.

Flooding and streamflow in the alluvial flat on 26 February 2019

This was shot just downstream of the spillover shown in the previous video. Here you can see where the spillover (foreground) rejoins the creek (background.)

Same area as above, two summers ago

Previously: 10 - 23 February - Ch-Ch-Ch-Changes Edition

Next: 24 February - 02 March - After the Flood Edition

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