Hidden Kent Lake and a popular waterfall
This area makes it easy to forget that the teeming hordes of the Bay Area are only a few minutes away. Kent Lake is tucked into the deep Lagunitas Creek drainage surrounded by ridges 1000' above, and this hike visits both the lake's edge and Alta Marin (I just made that up) for a nice tour of one of the wilder parts in the region.
This hike also travels through a diverse range of vegetation with everything from a few old growth redwoods to windswept grasslands.
The hike starts at, or rather under, the gate on the north side of Alpine Dam. Don't worry about going under because that is what you're supposed to do according to Johnny Law. There's a nice view of the larger-than-expected dam holding back Alpine Lake which is owned by the Marin Municipal Water District as is the entirety of this hike. Take the Kent Pump Road (a dirt fire road) from the gate as it heads down from the dam on a gentle grade 50-100' above Lagunitas Creek for 2.1 miles to its junction with the Old Vee Road (another fire road). This section is largely in a tall forest of redwood, Douglas fir and tanoak with views down to the left of what's left of the creek. There's not much to look at until the junction where the southeastern arm of the lake becomes apparent.
Continue on the Kent Pump Road as it winds along the southeastern corner of Kent Lake. The lake is intermittently visible as the fire road gently heads another 1.3 mile to its junction with the Little Carson Trail. Little Carson heads steeply uphill along its namesake drainage to Carson Falls 0.7 mile and 540' above, but I recommend continuing another mile to the pump house. This contraption consists of a sort of floating dock that sucks water from Kent Lake to be pumped underneath 1700' Pine Mountain to the San Geronimo Water Treatment Plant about 9 miles away.
The pump house has a floating contraption that looks like a floating dock with weathered pipes connected to pump house on the shore. There's a floating net ringing the dock with a 100' radius. There are a few places to get down to the shore over the last mile. There is what is obviously an old road that leads west from the pump house right into the lake. I wondered if there was a non-trail route from the end of the Kent Pump Road along the entire southeastern arm of the lake to the Pine Mountain Fire Road, but no way. It's a nice spot out in the sun with great views.
Return the way you came for a mile back to the Carson Falls Trail for the cardio portion of the hike. It only gets better from here. The Little Carson Trail relentlessly uphill through a deep forest of tanoak before reaching a flat area with a small meadow. There are some very large redwoods just past the meadow where the trail crosses Little Carson Creek along a nice wooden bridge. The cardio resumes as the trail steeply climbs up to the falls.
Carson Falls have 3 viewing areas along the trail. The lower spot is in a forest of tall tanoak, then travel up the trail about a hundred yards to the middle area which has a nice view of the top of the lower falls. The middle falls provide probably the best photography opportunities. The upper falls are easily viewed from above the pools at the trail's junction with the closed Old Sled Trail. I heard chirping frogs at all 3 spots, and saw California newts in 2. Carson falls is one of the last breeding sites of the foothill yellow-legged frog in Marin County, but luckily there was plenty of water in the pools around the falls on Sunday April 26, 2015 despite the brutal drought gripping California. There are even docents who monitor the falls in order to protect the falls, but I didn't meet any that day.
The climbing is almost over, but the Little Carson Trail climbs another 300' from the upper pools through an open area before switchbacking through a pretty tanoak forest. There are open grasslands at the bottom and top of this segment with spectacular views of Pine Mountain to the northwest, but the views are marred by a drooping power line that goes up and over the ridge you're about to crest down to the pump house. The upper end of the trail hits the Pine Mountain Fire Road at 1300', and the transition from deep forest to open grassland is quite sudden. Turn right on the road as it heads south for a quarter-mile to where the Old Sled Trail used to connect from the west (from the upper Carson Falls), but still continues to the west down to the Fairfax-Bolinas Hwy. to the east. Continue on the road until it becomes the Oat Hill Road, goes about a mile to the Old Vee Road. There are views in all directions with San Francisco Bay and the hilly East Bay to the east, Oakland to the south, and seemingly endless ridges to the north. The Pacific Ocean is even out there to the southwest. There are a few small copses of Sargent cypress in the spots with serpentine soil, but most areas with that greenish-grayish soil are mostly devoid of vegetation.
Old Vee goes a little more than a mile back down to the Kent Pump Road, and some stretches are very steep. This would be a nice cardio-heavy way to reverse this lasso loop. There is a monotype tanoak forest along much of the trail's left side just like the upper switchbacks on the Little Carson Trail. Turn left on Kent Pump Road to travel the 2 plus miles back to the dam through the forest of redwood and Douglas fir.
Gate Policy: If a gate is closed upon arrival, leave it closed after you go through. If it is open, leave it open. Leaving a closed gate open may put cattle in danger. Closing an open gate may cut them off from water. Please be respectful, leave gates as found.
WARNING! Hiking and outdoor related sports can be dangerous. Be responsible and prepare for the trip. Study the area you are entering and plan accordingly. Dress for the current and unexpected weather changes. Take plenty of water. Never go alone. Make an itinerary with your plan(s), route(s), destination(s) and expected return time. Give your itinerary to trusted family and/or friends.