Runoff Overview Tom Hopson

Basic runoff processes

Role in Flood Prediction Process

General Soil Water Processes

General Runoff Terms

Surface Runoff

Infiltration Excess Overland Flow

Saturation Excess Overland Flow

Interflow

Transmissivity Feedback

Soil-Bedrock Interface

Groundwater Ridging

Pre-Event Water

Contributing Area and Runoff Volume

Basin Size and Runoff Timing

Basin Shape

Stream Meanders

Basin Slope

Soil Properties

In Depth: Soil Formation Processes

Soil Texture Classification

Soil Composition

Soil Profile

Surface Properties

Runoff Modeling Concepts -lumped -semi-distributed -distributes

Complex Hydrologic Models For forecast applications, adding complexity not always warranted: -limited observations to constrain parameters -run the risk of over-calibration

Lumped Modeling Semi-Distributed Modeling

Distributed Modeling -Don’t precisely capture watershed due to discretization -better capture forcing spatial variability and response

Distributed modeling methods allow modeling of smaller and smaller basins. They also allow computation of more realistic runoff within a basin. Flash flood forecasts, for example, have improved with the implementation of distributed models. Distributed models do however require more complex and more high-resolution data, introducing more uncertainty.