ANS:D - All of these.

The rational formula for peak drainage discharge is a fundamental method used in hydrology to estimate the peak flow rate of stormwater runoff from a specific drainage area. It provides engineers and planners with a practical approach to design stormwater drainage systems and manage urban runoff. Let's explore the contributions of each individual associated with the evolution of this formula:

1. Fruhling:
   • William H. Fruhling was a civil engineer who made significant contributions to the field of hydrology. While he didn't directly develop the rational formula, his work laid the groundwork for its evolution. Fruhling conducted extensive research on rainfall-runoff relationships and the factors influencing stormwater flow rates. His studies helped establish the theoretical basis for subsequent developments in stormwater hydrology, including the rational formula.
2. Lloyd David:
   • Lloyd W. David, an American hydraulic engineer, contributed to the advancement of stormwater engineering principles. His research focused on the analysis of rainfall characteristics and the prediction of runoff from urban areas. David's work played a crucial role in refining the rational formula by incorporating factors such as rainfall intensity, duration, and watershed characteristics into the calculation of peak discharge.
3. Kuichling:
   • Rudolph Hering and John L. Kuichling were two hydraulic engineers who collaborated on the development of hydraulic engineering principles in the late 19th century. While Hering is often credited with the initial concept of the rational formula, Kuichling's contributions were significant in refining and popularizing the method. Kuichling expanded upon Hering's ideas and proposed a systematic approach to estimate peak discharge based on watershed characteristics, rainfall intensity, and duration.
4. All of these:
   • The rational formula for peak drainage discharge evolved through the collective efforts of multiple researchers and engineers, including Fruhling, David, and Kuichling, among others. Each individual contributed valuable insights and advancements to the field of stormwater hydrology, leading to the formulation and refinement of the rational formula as a practical tool for engineering practice.

In summary, the rational formula for peak drainage discharge represents a culmination of contributions from various researchers and engineers over time. While specific individuals may have played key roles in its development, the evolution of this formula is a collaborative effort aimed at improving our understanding of stormwater runoff and enhancing the design and management of drainage systems.