Runoff Processes Environmental Hydrology Lecture 10

Photo: B. Wemple

Why predict runoff? Estimate water supply (seasonal, annual) Estimate flood hazard, flood flows (event- based) Design infrastructure – detention basins, culvert sizing (“design storm”) Understand system behavior

The Hydrograph Source: U.S. Geological Survey,

The Hydrograph Ward & Trimble, Fig. 5.11

The Hydrograph Source: U.S. Geological Survey Ranch Brook at Ranch Camp, near Stowe, VT USGS

Runoff Production Horton overland flow time Infiltration rate, i (mm/hr) Precipitation rate, p (mm/hr) p > i  overland flow Robert E. Horton Image source: American Geophysical Union

Runoff Production Horton Overland Flow R5 Catchment, Oklahoma. Photo: K. Loague, Stanford Univ.

Runoff Production Variable Source Area model John D. Hewlett From: Jackson et al., Hydrologist : John D. Hewlett ( ), Hydrological Processes 19: Ward & Trimble, Fig 5.3

Runoff Production Variable Source Area model Source: Taiwan Forestry Research Institute

Geochemical indicators of runoff production Source: Burns et al., Quantifying contributions to storm runoff through end- member mixing analysis and hydrologic measurements at the Panola Mountain Research Watershed (Georgia, USA). Hydrol. Process. 15, 1903–1924 (2001)

Factors affecting runoff Precipitation- –Type, duration, amount, intensity Watershed Characteristics –Size, topography, shape, orientation, geology, soils Land use

Effect of development on runoff Ward & Trimble, Fig. 5.13

Lab: Measuring runoff Depart 11:15 a.m. kiosk on Carrigan Drive (east side of Aiken). Bring lunch, shorts, sandals. Return by 5:30pm. Read “How Streamflow is Measured” Read Wemple et al.,