Sediment Releases at Dam Removal Projects
| Sediment management is a critical component of dam removal projects, often shaping costs and community acceptance. For dams storing uncontaminated sediments, downstream release is frequently the most cost-effective and practical approach, with potential ecological benefits for sediment-starved downstream habitats. To adopt this strategy, project proponents must estimate the stored sediment quantity, erosion rates, and downstream sediment deposition locations and durations.
Join Matt Collins, a hydrologist and geomorphologist with the NOAA Restoration Center, who will present observations of a recent dam removal sediment release. Matt has extensive experience in habitat restoration monitoring and provides science support for restoration planning and design across the Northeast United States, specializing in stream sediment dynamics and climatic influences on streamflows important for fisheries resources and project design. The webinar will focus on the 2018 removal of Bloede Dam on Maryland’s Patapsco River. This 10-meter-high dam impounded approximately 186,600 m³ of sediment, composed of 70% sand and 30% mud. These proportions match estimates made during pre-removal engineering studies, but the total stored sediment estimate was about 20% less. The difference between estimates reflected a real change in stored sediment quantity between 2018 and 2012 when the engineering studies were completed, additional data available after removal, and different estimation methods. After removal, using elevation surveys generated by traditional methods as well as structure-from-motion (SfM) photogrammetry at high temporal resolution, Matt and his team documented rapid erosion of stored sediment in the first six months (~60%) and stable channel development in the impoundment during this phase, followed by greatly reduced erosion rates. Their findings were predicted by a two-phased erosion response model developed from observations at sand-filled impoundments, thus expanding its applicability to include impoundments with a sand-over-mud stratigraphy. A similar two-phase erosion response has been reported for sediment releases at other dam removals in the United States, France and Japan across a range of dam and watershed scales, indicating what practitioners and communities should expect in similar settings. Downstream surveys revealed that sediment transport occurred swiftly through a 5-km reach, particularly during periods of above-average discharge in the first year, with minimal overbank storage. This webinar will equip practitioners and community stakeholders with key takeaways for sediment management in dam removal projects, emphasizing realistic expectations and strategies for similar contexts.
12PM Eastern / 9:00 AM Pacific Duration: 60 Minutes Meeting ID: 955 7927 2228 Passcode: 133805 Important Note: Registration is not required; however, participation is limited to 300. Please sign on early. Space is available on a first-come, first-serve basis. Direct questions to Andy Peters andy@riverconnectivitysystems.com Past Webinars: For information on all of our past webinars, visit the Joint Committee’s Webinars page or our YouTube Channel where recordings of our past webinars are now available. |