Soil Liquefaction Hazards and Ecological Impacts in Coastal Wetlands of the Pisco River, Peru

Abstract. Coastal wetlands located in seismic regions can be highly vulnerable to soil liquefaction, a phenomenon where saturated, loosely compacted soils temporarily lose strength during earthquakes. This study investigates the relationship between soil liquefaction and the dynamics of coastal wetlands along the left bank of the Pisco River in Peru, a region affected by the 2007 Pisco earthquake. Through geotechnical field tests, satellite image analysis, and local interviews, we identified that wetlands and their adjacent areas – often with shallow groundwater and sandy soils – present high susceptibility to liquefaction. Affected wetlands showed both negative impacts, such as ground subsidence and vegetation loss, and in some cases, post-seismic ecological recovery due to groundwater rise. The results confirm that even degraded or filled wetlands retain subsurface characteristics prone to liquefaction, extending risk zones up to approximately 200 meters beyond current water boundaries. These findings highlight the dual role of wetlands as both vulnerable ecosystems and natural indicators of geotechnical risk. Future research should focus on integrating wetland conservation into seismic risk management and land-use planning. Recognizing the geotechnical memory of these ecosystems is key to avoiding infrastructure damage and promoting more resilient coastal development in earthquake-prone areas.