Simple and Accurate Assessment of the Danger Posed by Large Storm Events and Downstream Impacts Below Remote Dams

Heavy rainfall events, especially those that develop rapidly and unexpectedly, can lead to catastrophic impacts in both remote regions and densely populated areas. In the past, much of the effort to examine the potential for and the results of a large dam failure, have been focused exclusively on dams in urbanized communities with substantial remote sensing data. Additionally, Emergency Action Plans (EAPs) and evacuation warnings for critical dam infrastructure relied on current flood conditions and signs of failure prior to notifying emergency personnel and the population at risk. Owners and/or operators were responsible for real-time assessment, typically on-site, despite many dams being difficult to reach and potentially dangerous to inspect during rainfall events. Historically, the level of expertise needed to translate rainfall and runoff data in real-time is substantial and the effort can be extremely time intensive.
Now, with advances in our understanding of rainfall-runoff response and the accuracy of extended forecasts related to large storm events, impact predictions are possible with a high level of confidence. Applied Weather Associates (AWA) continues to collaborate with dam owners and regulators to develop highly accurate datasets for enhanced EAPs that include historic storm and flood events, characterization of large storm and flood events, and calculation up to the Probable Maximum Precipitation (PMP) and Probable Maximum Flood (PMF) events.
By evaluating prior storm and flood events, models can determine the likely rainfall-runoff response of watersheds, the potential threat to the public, and the potential loss of critical infrastructure. Also, by pre-determining the impacts of various return-frequency rainfall events, mitigation measures can be evaluated for multiple scenarios in advance. Additionally, rather than simply preparing static “worst-case” mapping of conditions like a PMF with dam failure, water surface elevations and inundation mapping can be created quickly with reported confidence limits for forecasted events. Predictions can be modified in real-time as an event approaches and the width of confidence intervals decreases.
Data for these models is available from quality-controlled sources and many of the models needed to determine the reaction of a watershed have already been approved by regulators internationally. The key is to combine weather prediction, the rainfall-runoff reaction of a watershed to prior events, a calibrated rainfall-runoff model, and the best available topographic and structural data along the impacted river. Limitations to the availability of rainfall and runoff data from remote sites in the past are now being addressed by AWA. This includes the integration of the Elysium Technology Water Sensor Suite (WSS). This unique sensor system, about the size of a shoebox, is incredibly cost effective, energy efficient, and simple to install in any location. It uses satellite communications, solar power, a rugged housing, and the ability to work with various sensors to produce secure data transmission through an intuitive customizable dashboard. The platform offers data from any location to confirm forecast models, report flood flows and rain volumes, check river and lake depths, and transmit other data critical to public safety and operations.
This paper will describe implementation of this suite of processes to monitor watershed and evaluate dam safety in remote locations world-wide, especially where power, communication, and historic data are scarce.