1. The document introduces arch dams and buttress dams. An arch dam is curved in plan and transfers most of the water load through arch action to the abutments, while the remainder is transferred through cantilever action to the foundation. 2. Advantages of arch dams include requiring less material than gravity dams of the same height, having minimal issues with uplift pressure due to their smaller base width, and being able to be constructed in locations with moderate foundations unsuitable for gravity dams. 3. Buttress dams are modified gravity dams with solid buttress walls constructed parallel to water flow at regular intervals, supporting an arch or inclined deck slab over the top to minimize the amount of concrete required compared to standard