ENVE-205 Environmental Engineering Hydrology

CHAPTER V: Watershed Characteristics and Infiltration

In this chapter, effects of topographical watershed characteristics such as slope and those of watershed soil characteristics such as permeability on the hydrograph shape formation from a discharge point will be discussed. Soil infiltration calculation methods such as Green-Ampt, NRCS, and Horton will be discussed in detail.

Study Plan:

· Learning the directly connected impervious area and not directly connected impervious area concepts (Section 5.1.1).

· Learning the effects of drainage system, land cover, and area storm coverage properties on the hydrograph shape (Sections 5.1.2, 5.1.3).

· Learning the “time of concentration” concept for overland flow, pipe flow, and channel flow conditions. In this context, Izzard’s Equation, Kerby’s Equation, and NRCS Equation for overland flow will be discussed. In addition, Manning’s Equation for pipe flow and channel flow will be examined (Sections 5.2.1, 5.2.2, 5.2.5, 5.2.8). Example problem 5.2 (see the additional information).

· Learning the NRCS hydrologic soil classification (Section 5.3.1). See Fig. 5.9.

· Learning the Green-Ampt Method in infiltration calculations (Section 5.3.2). See formula derivation. Example problem 5.3.

· Learning the NRCS Curve Number (CN) Method in infiltration calculations (Section 5.3.4). See formula derivation in Fig. 5.10. Discuss the moisture condition modifications for CN and composite curve number concept. Example problems 5.4, 5.5.

· Learning about the Horton’s Equation in infiltration calculations (Section 5.3.5).

· Learning the concepts of water quality such as pollutant load, event mean concentration, and loading rate (Section 5.5).

· See some infiltration measurement devices.

· Homework problems 1, 2, 3, 9, 12, 13.