The very low-gradient (flat) Cumba Valley continues, but in our case, Zacarias had volunteered (or been directed?) to row our boat. And, Karl was rowing the cataraft for CJ.
At Corral Quemado, the guys went up to the roadside food stands and returned with de-husked cold coconuts. The cold coconut milk was very refreshing.
As we left Corral Quemado, an upstream wind started blowing. It built steadily in intensity until finally we were enveloped in a sandstorm. Our boat was blown up against the shore, so both Kathy and I took the oars – one each. We battled our way downstream to where the group had pulled into the lee of a stand of cane. After a while it abated, and we set out again. Pedro found a sheltered backwater for camp, again sheltered by cane, at K. 552.
At the north (downstream) end of the Cumba Valley, at Rentema, the Rio Utcubamba enters from the east and the Rio Chincipe, which rises in Ecuador, enters from the west. This greatly increases the volume of the river, as it enters the Jungle Marañon section.
At last! We exited the valley (that we thought would never end), the Cumba Valley, and entered a limestone canyon. Immediately, the vegetation began to change and increase in density. In the first few miles of travel through this new canyon, we transitioned into low-elevation rainforest, or “La Selva” (the elevation at Rentema is 1300′). How to explain this? My guess is that the river canyon acts as a conduit for warm, moist air that originates downstream in the yet lower “real” Amazon jungle.
In the Jungle Marañon, canyon sections that contain rapids are called “pongos”. The first one we encountered is called the Pongo de Rentema.
We arrived in early afternoon at the first large rapid – Amojado (III-IV), at K. 596 – and the site of Camp #27. This rapid is formed by the delta of the Rio Amojado, which enters from the right. Just downstream is a bridge and the town of La Libertad. We wanted to get there early so that the kayakers had ample time to surf the large hole seen in the photo below (extreme upper right). Because of the increase in volume provided by the two tributaries that entered at Rentema, holes larger than anything seen upstream were now available – and this one was a beaut! As will be seen below, Nate, Pedro and Barba had the time of their lives, getting the best surfs of the trip.
What is kayak surfing? To answer this question, I should first point out the difference between ocean waves and river waves. Ocean waves move through the water. River waves most often stay in place, as the water moves through them. River waves are formed in three general ways.
1. Waves are formed when water speeds up and gains more kinetic energy, such as when the channel is constricted. Constriction of the channel is seen in the photo above, at the top of the rapid.
2. A wave is formed as water passes over a rock (or drops off a ledge), and then rebounds. What does “rebound” mean, in this instance? If the drop on the downstream side of the rock is not particularly steep, the water bounces up as a wave. If the drop is steep, the rebound takes the form of an eddy on a vertical plane, in which the water first bounces up vertically and then falls forward and back upstream. River-runners call this a “hole”, which hole is formed by the downward falling slope of water on the upstream side, the upward and forward-moving slope of water on the downstream side and the trough that is formed between the two.
3. A less-common type of wave is caused by sand dunes building up on the bottom of the river. These sand dunes usually form in a series, as do the “sand waves”. The sand dunes build up and collapse in the space of a minute or minutes, as do the waves that reflect off of them.
As is the case for surfers on ocean waves, gravity pulls the surfing kayaker forward and down the face of the wave. For the river kayaker, however, there is the additional boost provided by the upstream-moving slope of water found on the downstream side of the hole. Big holes attract proficient kayak surfers, for the extensive “rides” that can be had on this forward-moving slope of water. While this is true for kayakers, I should point out that such holes are avoided by rafters. Earlier in this series of posts (Day 10, Llamara Rapid), I mentioned that our raft got “surfed”, injuring Kathy in the process. This occurred when our raft dropped steeply into a hole (twice, in the one rapid!), and got trapped. The steep slope of upstream-moving water held us in place until the boat was filled (with water) and became heavy enough to counteract the forces holding us in. On popular rivers, one often finds certain infamous holes that trap (and sometimes flip) rafts so frequently as to be called”keepers”. One such is Seidel’s Suckhole, on the Arkansas River, in Colorado.
Fortunately for this wordy discussion, illustrative examples are here provided. BTW, the hole that our kayakers chose to “play” in, seen below, is sufficiently powerful to both trap and then flip a raft.
Barba gets a good ride.
Pedro goes sideways
Taken from a lower vantage point, the following two photos illustrate the depth of the hole.
Also at Camp #27:
The following post: