洪水易发性制图（FSM）对于灾害预防至关重要，但在缺乏数据的地区仍具挑战性，因为水动力模型需要密集的地球物理输入。本文提出ZeroFlood，一种用于数据高效洪水易发性制图的地理空间基础模型框架。该方法通过基于模态思维（TiM）的推理对地理空间基础模型（GFMs）进行微调，实现仅依赖基本地球观测数据（如Sentinel-1或Sentinel-2影像）进行洪水预测。利用数据丰富区域的配对地球观测数据与模拟洪水地图，ZeroFlood通过跨模态表示学习弥合数据差距。基于TerraMind和Prithvi GFMs的实验表明，TiM提升了模型鲁棒性，其中TerraMind-Large配置的F1得分为67.21。结果证明了基于基础模型的FSM在洪水风险管理中具有可扩展性和数据高效性。

Flood susceptibility mapping (FSM) is vital for disaster prevention but remains challenging in data-scarce regions where hydrodynamic models require dense geophysical inputs. This work introduces ZeroFlood, a geospatial foundation model framework for data-efficient FSM. The approach fine-tunes Geospatial Foundation Models (GFMs) with Thinking-in-Modality (TiM) reasoning, enabling flood prediction from basic Earth observation data such as Sentinel-1 or Sentinel-2 imagery. Using paired EO and simulated flood maps from data-rich regions, ZeroFlood bridges data availability gaps through cross-modal representation learning. Experiments with TerraMind and Prithvi GFMs show that TiM enhances model robustness, with the TerraMind-Large configuration achieving an F1 score of 67.21. The results demonstrate the feasibility of foundation-model-based FSM as a scalable and data-efficient solution for flood risk management.