(Courtesy of the California Department of Water Resources).
Last week California’s Oroville Dam, the tallest dam in the United States, almost failed due to a surplus of water filling Lake Oroville. As the lake filled higher and higher, water was being released, via spillways, into the Feather River. The volume of water caused erosion of the dam’s main spillway, causing it to crater and break apart. As a result, the dam’s emergency spillway began to erode. That spillway had never been used and was unlined. The lack of concrete lining may have led to its erosion as well.
Nearly 200,000 people were evacuated from the area, many of them fleeing to higher ground cities like Sutter. As the water began to recede, residents began to travel back home.
But what went wrong? What caused the damage in the first place? Continue reading
Protecting properties on coastal parcels is critical, especially as we start to see much of our nation’s coastal areas affected by rising sea levels. Higher sea levels are allowing the tides to carry away much of the natural defenses and sands that keep properties and beaches protected from the oceans, especially during heavy coastal storms. In fact, some coastal communities are running out of beach sand due to global warming.
What can coastal property owners do to protect themselves? The answer is installing or improving existing seawalls. A bulkhead, also known as a seawall, helps prevent erosion of land area or damage to structures by placing a barrier between the sea and land. Seawalls protect properties and beaches against damage from wind, wave and ice forces. They may feature curved or flat-facing surfaces, and can be comprised of gravity retaining walls, cantilever retaining walls, and pile-supported retaining walls. New seawalls are commonly constructed of concrete, but older seawalls included materials like stone, an excellent buffer against wave energy. Continue reading
Living near the ocean is a dream for many, but the reality can be anything but. Property damage or loss caused by coastal bluff erosion can destroy the reward of a lifetime of hard work. First, what is a coastal bluff and what can happen to a property when erosion occurs? Coastal bluffs consist of the entire slope that lies between a marine terrace and the sea. They are formed when there’s a rapid uplift of the shore relative to sea level. Erosion is a natural process that occurs to bluffs over time and through various mechanisms, leading to instability.
Coastal bluffs are subject to erosion via several mechanisms, including creep, sheetwash, rilling and gullying and sudden collapses. Creep refers to the slow, downslope movement of a mass of sediment. A large factor in the promotion of creep is groundwater seepage, and engineering solutions include irrigation restriction and the installation of horizontal drains, or hydroaugers, and pumping wells. Continue reading