RESPONDING TO LANDSLIDE EMERGENCIES: COMMUNICATING WITH STAKEHOLDERS AND THE FEEDBACK LOOP OF PREPARATION, RESPONSE, ANALYSIS AND LESSONS LEARNED (Invited Presentation)

Since 1990 the North Carolina Geological Survey has responded to over 160 landslide events involving ~350 landslides in the Blue Ridge Mountains of North Carolina, including those resulting in fatalities, injuries, destroyed and damaged homes, and threats to regional infrastructure. Responses involve communicating with first responders, the public and the media, and giving expert witness testimony in cases involving litigation. A primary objective is to provide stakeholders with timely, unbiased, scientific information to help protect public safety and property. A key response function is to help increase situational awareness for emergency responders. Post-landslide efforts include assistance with damage assessments, contingency plans if unstable slopes remain a threat, and documentation to support recovery and mitigation funding.

Investigations revealed that in many cases damaged homes and critical facilities had been built in areas vulnerable to landslides. Slope modifications by human activity were contributing factors in many cases, including fill failures that mobilized into destructive debris flows. Most landslides occurred during heavy rainfall from tropical cyclones, low pressure systems (e.g., atmospheric rivers), and warm weather convective storms, especially when coincident with periods of above normal rainfall. Correlations with rainfall indicate that debris flows originating on modified slopes can be triggered by rain events with lower rates and durations than those that trigger debris flows on unmodified slopes. These findings show that smart development can help reduce losses from landslides and thereby improve communities’ resilience after landslide events. Field computers, lidar digital elevation models, orthophotography, satellite imagery, and uncrewed aerial systems used in conjunction with a landslide geodatabase have improved pre-response preparation, data collection and analysis, and delivery of geospatial data to stakeholders.