For years I followed the Klamath Dam removal proposal. The Klamath River flows from Oregon through California, cuts through the Cascade Mountains, and empties into the Pacific. The dams on the Klamath are a classic case of a bunch of old dams (built as a result of Congress’s authorization of the Reclamation Act of 1902) making an unnatural mess both environmentally and economically. It is probably where the term “farmers versus fish” comes from. Building hydroelectric dams with reservoirs on the Klamath River provided irrigation water and cheap electricity for farmers. However it decimated the fish population. Enforcement of the Endangered Species Act (authorized by Congress in 1973) required dam operators to release a minimum flow of water from the dam reservoir to protect three different endangered fish downstream, including the Coho Salmon. There was a big uproar during the first decade of the 21st century when drought in the Klamath River Basin resulted in a cutoff of water for irrigation to farmers in order to protect the endangered fish (fish 1, farmers 0). Then there was an Administration change in the White House and the minimum water flows from the dam reservoir sustaining the endangered fish were reduced and more water was released for irrigation purposes (fish 0, farmers 1). Reduction of minimum flows led to a huge fish kill of Coho Salmon and restrictions on salmon fishing in the Pacific Ocean. In all cases people were ticked. Farmers were ticked, fishermen were ticked, native tribes who depend on fish for subsistence living were ticked, environmentalist were ticked.
Then the electric company who operated the dams decided that providing hydroelectric power from the Klamath dams wasn’t very economic. From what I recall, the electric company wanted to raise electric rates by about a 1000 percent. As you can imagine, that didn’t go well for the company at all. Then re-licensing of the dams came up, and the company decided the dams weren’t worth operating anymore. So, this all led to a proposal to remove the dams. There was a whole lot of uproar about that too. But interested parties, meaning the states of California and Oregon, native tribes and the electric company came to an Agreement in 2010 to seek removal of the dams. Unfortunately, nobody wanted to pay for the dam removal. I think there was some federal legislation proposed around 2014, but the estimated costs were pretty astronomical and the legislation has gone nowhere. If it ever gets passed, it will be the largest dam removal project in the United States. And it will give us the results of what the environmental impacts of a dam removal to a major river system will be.
Right now we don’t have the answers to what the actual environmental impacts of dam removal are. There are studies of course, which outline what scientists believe will happen. But the actual studies of what really happens after dam removal are pretty limited. There are a number of dams around the country which have been removed, but up until the last ten years no one has been studying the effects of dam removal on changes in sediment transport and stream morphology or changes in plant and fish communities. For instance, there’s a dam removal program in Massachusetts. I’ve heard a number of talks at restoration conferences about efforts to restore streams in Massachusetts. Massachusetts has been highly populated by non-native people for quite awhile. They are the Plymouth Rock folks who came over on the Mayflower. Once these non-native people arrived, they started damming streams and rivers up – mostly for mills; first flour mills then textile mills. They have some 3000 dams in the state, many built between the 17th and 19th century. Can you imagine? Many of these dams are not even functioning for any purpose, but they are still there mucking up fish habitat and natural stream functions.
Massachusetts has an aggressive dam removal program, but if you go to look for reports on the impacts after the dam is removed, you will not find any. You’ll find feasibility studies for the removal of a dam, you’ll find studies of the contaminated sediments existing in many of the dams in the industrial areas in eastern Massachusetts, and you’ll even find records of community input to dam removal. But I’ve yet to find a report documenting changes to a stream or river after a dam was removed in Massachusetts. There’s probably a reason why. It cost money to study a stream or river system after the dam is removed. Also everybody thinks dam removal will restore natural stream functions, so why bother to study the actual results. The lack of information on the impacts of dam removal has been so great, that the Gulf of Maine Council on the Marine Environment put together a document in 2007 outlining procedures for monitoring the outcome of dam removal. It is entitled “Stream Barrier Removal Monitoring Guide” (http://www.gulfofmaine.org/streambarrierremoval/). Massachusetts is one of the American states whose river systems empty into the Gulf of Maine. The Council cited lack of post dam removal monitoring data nationwide as a reason for establishing monitoring procedures. It has been the “hue and cry” of restoration specialists everywhere that there is money for restoration but no money for monitoring the results of restoration to see whether the efforts have succeeded and to what extent.
The Council’s guide is a pretty good one, especially when examining the hydrological impacts of dam removal. The guide’s monitoring parameters include such items as establishing monumented crossections downstream of the dam, conducting longitudinal profiles of the stream, and determining sediment grain size distribution. Cross sectional profiles will document how the stream banks and channel width adjusts to post dam removal flows and the increases in sediment being transported by those flows. The longitudinal profiles along the length of the stream will show how the channel slope is adjusting to the dam removal and what natural stream characteristics like pools and multiple channels are being created. And sediment grain size distribution studies will help determine whether you are getting more fine sediment in the channel and whether the newly free flowing stream has the power to move coarser sediment further downstream. These are all terrific ways to tell if your stream or river system is righting itself to pre-dam conditions.
The only full studies I have ever seen of post dam restoration are from the Elwha Dam removal in Washington State. Actually there were two dams on the Elwha River – the Elwha Dam and the Glines Canyon dam. The dams were built back during the dam building heydays of the early 1900’s. The Elwha River flows north out of the Olympic Mountains into the Strait of Juan de Fuca. It’s outlet into the straits is just a little west of the town of Port Angeles, which I like to think of as the gateway town to Olympic National Park, but other people know it better for its ferry service to Victoria, British Columbia. The two dams sat right in the Olympic National Park and the Park Service has lots of great photos of the dams and the dams being removed (http://www.nps.gov/olym/learn/nature/elwha-ecosystem-restoration.htm.) The dam removal began back in late 2011 so they are gone now. Several years worth of post dam removal data has been collected. I pulled out some recent papers on the results. They are actually quite phenomenal. Probably the best one was published in 2015 in the journal Geomorphology. Geomorphology for all of you non-scientists is the study of landforms and how they developed. It was one of the first geology classes I ever took and it is a fascinating subject. You get to examine all sorts of topographical and geologic maps, aerial photos and satellite images. So the paper (referenced below) was on coastal geomorphic changes as a result of the dam removal.
First of all, the Elwha is a short river. It is less than fifty miles long. Coming off the north face of the Olympic Range, its vertical profile (as you can imagine) is quite steep. Studying such a steep river by conducting the kind of longitudinal, cross sectional, and grain size studies downstream of the dam, which are recommended in the “Stream Barrier Removal Monitoring Guide” referenced above, would be seriously hard and probably of little use. But studying the output of the river to its delta in the Strait of Juan de Fuca will tell you a lot. Beaches and land on the strait near Port Angeles have been eroding for some time. The dams have been storing up all the sediment coming off the north slope of the Olympic Mountains in the Elwha River Basin and robbing the shoreline. The study states there was 20 million cubic meters of mud, sand and gravel stored in the reservoirs behind the two dams. The study further estimated, based on the accumulation of sediment in the reservoirs, 240,000 cubic meters of sediment a year was prevented from being carried down the Elwha River to the delta and shoreline. This is a lot of sediment. The delta and beaches were essentially being starved and the constant erosion by tidal currents and waves was taking its toll on the shoreline.
During the first year of dam removal the researchers measured 113,900 cubic meters of new sediment deposition on the delta, beaches and seafloor. This is five times what was being deposited before dam removal. In addition, the researchers measured changes to the delta found at the mouth of the river. They found the delta had increased in size by 100 meters. During the second year, researcher measured 2,221,000 cubic meters of new sediment deposited on the delta, beaches and sea floor. This increased sediment accumulation and extended the delta at the river outlet another 200 meters offshore. Shorelines east of the river mouth were measured to have extended an average of 40 meters into the strait. With all this new sediment, researchers saw some big changes on the sea floor. Before dam removal the seafloor was rocky, because no fine sediments from the river were entering the strait. The rocky seafloor supported a lot of different kelp species. With the increase in sediment, the kelp population is decreasing. The researchers reported the area was moving toward a river dominated geomorphology, just as it was nearly a hundred years before the dam was built. So, it looks like in the case of the Elwha River, natural processes are being restored once a dam has been removed.
Here’s the full reference for the Elwha Dam Removal: “Large Scale dam removal on the Elwha River, Washington, USA: Coastal Geomorphic Change”, Guy Gelfenbaum, Andrew Stevens, Ian Miller, Jonathan Warrick, Andrea Ogston, Emily Eidam, Geomorphology, Vol 246 (2015), pp. 649-668.