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Tag: civil engineering

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    Fish Ladders Keep Species Swimming

    Dams often use fish ladders to help migratory species make their way upstream without interruption. In this video, Grady from Practical Engineering discusses some of the considerations that go into this special infrastructure and what kinds of designs work for different species. The first challenge for any dam is attracting fish to the ladder, which is often done by regulating the water flow at the entrance to create the velocity and turbulence that fish look for when going upstream.

    Once fish are in the ladder, they travel up a series of jumps that break the dam’s elevation into manageable steps. Different dams use various baffle designs to create jumps suited to their local species and the way they like to swim. Calmer spots in each section give fish a spot to rest before they carry on. In well-designed systems, the vast majority (97%!) of fish that enter a ladder make it through to the other side. (Video and image credit: Practical Engineering)

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  • Ancient River Branch Discovered Near Giza Pyramids

    Ancient River Branch Discovered Near Giza Pyramids

    Today the pyramid complex at Giza sits kilometers from the Nile River, raising longstanding questions about how ancient builders moved the enormous stones that make up each structure. A new study using radar satellite imagery, geophysical data, and deep soil coring identified a previously unknown ancient branch of the Nile that ran alongside the Giza Pyramids as well as pyramids at sites to the south. The team’s data indicate that, during the era of the pyramids’ construction, the river would have flowed for over 60 kilometers with a maximum width of nearly 700 meters. Having such a substantial waterway right next to the pyramid sites would have drastically simplified the logistics of moving stones and workers during construction. (Image credit: A. Bichler; research credit: E. Ghoneim et al.; via My Modern Met)

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    Helping Fish Bypass Hydro Power Dams

    Many dams in the U.S. were built at a time when their ecological impact was not a major concern. But, thanks to ongoing efforts to study affected species and upgrade infrastructure, many dams now balance human energy needs with the needs of non-humans, like migratory fish populations. In this video, Grady from Practical Engineering takes us behind-the-scenes at McNary Dam in the Pacific Northwest, where special plans and equipment help adult fish swim upstream and juvenile fish pass downstream with as little impact as possible. It’s impressive just how widespread and thorough their infrastructure for letting fish and lampreys through is! There are even facilities to help naturalists track and study the populations passing through. (Video and image credit: Practical Engineering)

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    The Channel Tunnel

    To celebrate the 30th anniversary of the Channel Tunnel, Practical Engineering takes a look back at the construction and operation of this incredible piece of infrastructure. This 30-mile-long underwater tunnel began construction in the 1980s, using giant Tunnel Boring Machines to drill out three tunnels, starting from either side and, incredibly, meeting in the middle. All that construction underground (and underwater) is no simple feat, as Grady discusses. He also takes a look at some of the operational challenges of the design, including managing heat and air pressure build-up. (Image and video credit: Practical Engineering)

  • Remembering Rivers Past

    Remembering Rivers Past

    Our landscapes have changed dramatically over the last 200 years of urban development, but traces of the land’s past still remain. Many streams and rivers that once ran on the surface persist in underground culverts. Bruce Willen’s “Ghost Rivers” installation highlights the path of one such waterway, Sumwalt Run, which flows across what is now the Remington and Charles Village neighborhoods of Baltimore. The project includes ten installations that describe the hidden water and its history as well as a wavy, blue line that marks its path. (Image credits: Public Mechanics and F. Hamilton, see alt text; installation: B. Willen; via Colossal)

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    Do Droughts Worsen Floods?

    In recent years many areas have seen record droughts followed by sudden, massive rainfalls. Such wild swings raise the question: does drought-parched soil make flooding worse? That’s the question Grady tackles in this Practical Engineering video, and, as is often the cause in real-world engineering, the answer is complicated.

    How quickly water soaks into the spaces between soil particles depends on many factors, including soil type, vegetation, and how much moisture is in the soil already. In general, dry soils initially soak water in more quickly than pre-moistened soil – except when the surface soil is hydrophobic and water-repellent. Check out the full video to learn more! (Video and image credit: Practical Engineering)

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    Desalination in Action

    Desalination — the removal of salt from water — is an important process for providing the fresh water we need, but it’s quite expensive in terms of energy. In this Practical Engineering video, Grady demonstrates small-scale versions of the two most common methods for purifying water: distillation and reverse osmosis.

    In distillation, salt water is boiled to separate the water into vapor that’s then condensed into freshwater. As straightforward as that sounds, though, the process is expensive, requiring a lot of energy for relatively little (albeit extremely pure) water. In contrast, reverse osmosis produces a somewhat less pure product at a lower energy cost. But it also produces brine, an even-saltier water that must be disposed of. (Video and image credit: Practical Engineering)

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    Withstanding Rocket Launches

    It takes a lot of power to lift a giant rocket‘s payload all the way to orbit, and in the first moments of a rocket launch, all that energy is directed downward at a concrete pad. How do engineers design and protect launch pads? In this Practical Engineering video, Grady tackles just that question through a comparison of SpaceX’s Stage Zero and NASA’s Launch Pad 39A.

    SpaceX notoriously chose to build Stage Zero without a trench or water sprayer system like the ones NASA use. Trenches deflect the rocket exhaust to reduce the impact on infrastructure beneath the engines. And water sprayers reduce the temperatures the pad experiences and disrupt shock waves that otherwise hammer the pad. Without those precautions, even special heavy-duty concretes have a hard time holding together against a launch. (Video and image credit: Practical Engineering)

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    Mitigating Urban Floods

    For densely-populated urban areas, floods are one of the most damaging and expensive natural disasters. We can’t control the amount of rain that falls, so engineers need other ways to mitigate damage. It’s not usually possible to remove people and property from floodplains, so instead civil engineers look below the surface, building flood tunnel networks to alleviate floodwaters. In this Practical Engineering video, Grady demonstrates how these systems work and what some of their challenges are. (Video and image credit: Practical Engineering)

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    Why We Can’t Control Rivers

    Rivers are systems in a constant state of change, balancing flow speeds, path length, sediment deposition, and erosion, as seen in this previous Practical Engineering video. The next video in this mini-series considers what human interventions do to rivers. As convenient as it is for humanity to force a river into a straight and constant course, the long-term effects can be incredibly destructive both upstream and downstream.

    In this video, Grady takes a look at several types of interventions: stream straightening, dams, river crossings, and more. With the help of a stream table, he demonstrates just how these efforts shift the river’s balance and what effects — in terms of erosion, deposition, and flooding — each can cause. These disadvantages, along with habitat destruction, are part of why stream remediation projects are on the rise. (Video and image credit: Practical Engineering)