Coastal multi-hazard assessment and management of chronic geomorphological degradation in Pemalang, Indonesia

Abstract The coastal area of Pemalang Regency, Indonesia, faces escalating multi-hazard threats exacerbated by climate change, yet it remains an under-prioritized region for disaster management. This study analyzes the coastal characteristics of Pemalang and assesses multi-hazard levels using the Coastal Hazard Wheel (CHW) approach, evaluating parameters such as geological layout, wave exposure, tidal range, flora, sediment balance, and storm climate. Results reveal a heterogeneous landscape experiencing chronic geomorphological degradation. The coastal area is characterized by protected wave exposure and microtidal dynamics; however, driven by widespread volumetric sediment deficits, 73% of the shoreline is undergoing severe planimetric erosion, primarily concentrated in the eastern deltaic regions. Through the CHW framework, five distinct coastal typologies were identified, i.e., sedimentary plains (PL-14, PL-16), deltas (DE-14, DE-16), and river mouths (TSR), each exhibiting varying hazard profiles. Ecosystem disruption and inundation intensities range from moderate to very high, while saltwater intrusion and tidal flooding hazards are classified as moderate to high. The findings highlight critical hazard hotspots in deltaic and river mouth zones, where anthropogenic pressures and sediment deficits create cascading hazards. Ultimately, this study prioritizes 22 management interventions, advocating for a transition from administrative-based zoning to a hybrid strategy that integrates Nature-based Solutions (NbS) with structural flood-proofing. These results provide a strategic blueprint for government authorities to implement adaptive management and enhance long-term coastal resilience in Pemalang.