WASHINGTON, Sept. 9 (TNSLrpt) -- The U.S. Geological Survey issued Professional Paper 1909, 'Resurvey of the Marble Canyon and Bridge Canyon Dam Sites in Grand Canyon National Park--Changes in Sediment Storage and Evidence Supporting the Occurrence of Bedrock Incision Through the Mid-20th Century,' by David J. Topping, Joseph E. Hazel Jr., Matt Kaplinski and Paul E. Grams. The 89-page report, issued in 2026, compares historical Bureau of Reclamation dam-site surveys from the 1940s and . . .

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