Speaker
Description
Introduction: Asteroid impacts can cause varying levels of damage across different areas, largely depending on the energy of the impactor. The complex processes that cause damage are not limited to the initial effects. First-order effects (those that are triggered directly) such as blast waves, craters, ejecta plumes, seismic activity, and thermal radiation have been the primary focus areas of planetary defense studies [1-4], while second-order effects are still relatively poorly characterized [5]. Such cascading hazards could persist for years post-impact, and our understanding of them may be significant to long-term mitigation planning and recovery strategies. Downstream post-impact flooding has been predicted from the more common and well-understood terrestrial wildfire-flood sequence [5]. Thermal radiation due to impact is proposed to be analogous to wildfire effects, which causes hydrophobic damage to the surrounding soils, leading to an increase in precipitation runoff and consequently raising downstream flooding risk.
Approach: This work uses GeoCLAW, a model that solves the shallow-water equations [6], to evaluate potential downstream flooding events and assess their probability, magnitude, and relevance to flood risk assessment. A research framework was developed using a hypothetical impact scenario derived from the 2023 PDC (Planetary Defense Conference) risk corridor [7]: an 800 m-diameter asteroid impacting into the Dallas-Fort Worth area of Texas [8]. Estimates of the exposed and affected population were compared across different rainfall rates and the extent of soil surface hydrophobicity, induced by impactor heat. This comparison aimed to evaluate the influence of each factor on overall flooding risk. This methodology is then also applied to the 2025 PDC scenario’s roughly 200 m-diameter asteroid impact, providing contrast to the Texas case study, with significantly varying topography, infrastructure, and precipitation regimes present.
Current Application: This study compares two impact sites – one near Cape Town, South Africa (a coastal region with floodplains surrounded by mountains) and another upstream of Bucharest, Romania (a mountainous region with high drainage density) – to better understand when and where downstream effects may be more hazardous than initial effects. The findings emphasize situations where large population centers are located downstream from impact sites in less-populated areas. By determining the differences in flooding severity between these events, we can more accurately characterize the influence of impact location on local factors. These assessments aim to increase preparedness for such events, streamlining the evaluation of downstream flooding risk significance based on geography and predicted impactor attributes.
References:
[1] Hills, J., & Goda, M. (1993) AJ 105(3), 1114–1144.
[2] Collins, G. S., Melosh, H. J., & Marcus, R. A. (2010) MPS 40(6), 817–840.
[3] Mathias, D. L., Wheeler, L. F., & Dotson, J. L. (2017) Icarus 289, 106–119.
[4] Rumpf, C. M., Lewis, H. G., & Atkinson, P. M. (2017) GRL 44(8), 3433–3440.
[5] Titus, T. et al. (2023) NH 116, 1355–1402.
[6] Berger, M. J. et al. (2011) AWR 34(9), 1195–1206.
[7] Wheeler, L. et al. (2024) AA 216, 468–487.
[8] Titus, T. et al. (2023) IAA-PDC.