What additional information aside from floodplain data is crucial for a hydraulic study?

For a hydraulic study, cross-section information is essential because it provides detailed data about the geometry of a waterway, including the shape and slope of the riverbed or stream channel. This information is crucial for understanding how water flows through the area, how it interacts with surrounding landscapes, and how floodwaters might behave under different conditions. Cross-sections allow engineers and planners to model the hydraulic characteristics of the environment accurately, which is vital for evaluating flood risks, designing flood control measures, and making informed land-use decisions.

While other choices may present relevant considerations, they do not directly contribute to the hydraulic modeling of water flow as effectively as cross-section information does. For instance, historical flood records provide valuable context and data on past flood events, but they do not directly inform the hydraulic calculations required for modeling current conditions. Similarly, public safety protocols and economic impact analysis are important for broader floodplain management and risk mitigation strategies but do not provide the technical data necessary for hydraulic studies.