本文介绍公路小流域桥涵由设计暴雨推求洪峰流量计算方法的新途径。文中提出了以暴雨洪水的物理成因分析为基础的推理公式。根据公路小流域桥涵的特点,吸收了以往小流域暴雨洪水计算方法的经验,有所创新。对推理公式中的核心参数μ、τ建立了表达不同物理现象的数学模式,能较好地反映不同地区条件下暴雨特性。为了多种公式论证,同时提出了经验公式。两种公式能较好地解决无实测流量地区的设计流量计算问题。推理公式法为主,经验公式为辅,设计暴雨洪水已编制成各种图表,便于提供小桥涵设计洪峰流量推求、查算。 This paper introduces a new way to calculate the peak flow rate by design torrential rain in bridges and culverts of highway small watershed. In this paper, the reasoning formula based on the physical cause of storm flood is put forward. According to the characteristics of bridges and culverts in the small watershed of the highway, we have absorbed the experience of the calculation methods of storm floods and floods in the small watershed in the past and made some innovations. The mathematical model expressing different physical phenomena is established for μ, τ, which is the core parameter in the reasoning formula, which can well reflect the characteristics of rainstorm in different regions. In order to demonstrate a variety of formulas, we also present empirical formulas. The two formulas can well solve the problem of design flow calculation in areas without measured flow. Reasoning formula method, empirical formula, supplemented by the design of storm flood has been compiled into a variety of charts to facilitate the design of small bridges and culverts to calculate the peak flow, check.