What is required to determine the area that contributes runoff to a drainage system?

To determine the area that contributes runoff to a drainage system, it is essential to assess the dimensions of the surfaces that play a role in generating runoff. This involves analyzing the size and type of impervious (such as roads, roofs, and pavements) and pervious surfaces (like lawns and gardens) within the area. Understanding the dimensions allows for accurate calculation of the runoff potential, which is crucial for designing an effective drainage system that can handle the expected water flow.

While calculating the total length of drainage pipes, evaluating rainfall patterns, and identifying soil types are important factors in overall drainage planning, they do not directly contribute to identifying the area that generates runoff. Pipe length pertains more to the structural aspects of the drainage system, rainfall patterns provide insight into water volume over time, and soil type may influence water absorption rather than the direct measurement of contributing runoff area. Therefore, assessing the dimensions of the contributing surfaces is the primary step in runoff determination.