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Flash Flood Protection: Logan Dry Canyon, UT


HydroLearn

Problem Statement

Flash flooding is a hazard in many parts of the world. In south Louisiana, the terrain is particularly flat with minimal natural slope to support efficient drainage. Flash flooding is common in urban areas where runoff from rainfall quickly accumulates in coulees and cannot drain fast enough. A flash flood is a sudden and rapid rise in stream water depth resulting from heavy, localized rainfall. With a growing population, developing neighborhoods in terrain susceptible to flash floods has become more common and therefore increased the potential for damage to private property and public infrastructure.

Hydrologists are frequently required to design flood protection infrastructure to protect people and property from the impacts of flash flooding. An important hydrologic question in designing for flood protection is: How much streamflow occurs in a river in response to a given amount of rainfall? To answer this question we need to know where water goes when it rains, how long does water reside in a watershed, and what pathway does water take to the stream channel. This module addresses these questions and also looks at how much runoff is generated from surface water input comprised of rainfall.

Module Overview

In this module you will use the engineering design process to design a detention basin for use in protecting an area of urban development from flooding. In doing so, you will learn about specific topics in hydrology. The sections of the module are organized in conjunction with the steps of a typical design process, including data gathering and analysis, design using hand calculations and computer software (HEC-HMS).

This will be accomplished through activities within each section as described in the figure below. Results from each activity will be recorded in specified results templates. The results templates for each activity can be found at the beginning of each activity and also here. The results templates are organized such that results from one activity can easily be used in successive activities.

Topics Covered

-Watershed Properties

-Precipitation Analysis

-Runoff and Infiltration

-Inflow and Outflow Hydrographs

-Reservoir Design

-Modeling with HEC-HMS

Prerequisites

N/A

Learning Objectives

At the end of this case study, a student should be able to describe and implement the steps involved in:

-delineating a watershed

-acquiring and analyzing precipitation and soils data

-developing a design storm hyetograph

-developing a runoff hydrograph

-designing a detention basin to provide flood protection

This will be accomplished through activities within each section as described in the figure below. Results from each activity will be recorded in specified results templates. The results templates for each activity can be found at the beginning of each activity and also here. The results templates are organized such that results from one activity can easily be used in successive activities.

Course Authors

David Tarboton, PhD, PE

Professor, Utah State University. Contact: dtarb@usu.edu

Madeline Merck

Graduate Research Assistant. Contact: madeline.merck@aggiemail.usu.edu

Target Audience

Junior/Senior Hydrology and Water Resources Engineering Courses

Tools Needed

Computer with access to Internet, Excel, and free HEC-HMS software

Expected Total Hours

A student could expect to complete this module with approximately 15 work hours.

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