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Introduction

This Seminar CD series is intended to serve as an overview of stormwater management topics.  It includes theory, fundamental concepts, and practical applications.  Due to site specific geographic characteristics of the location of the sample applications, some of the methods and procedures may not be applicable to other locations.  Although the fundamental concepts are expected to apply, the user may need to coordinate with local authorities for suggestions or guidelines for methods and procedures commonly used in their site area.

This six (6) CD Disc set contains the same class materials provided at the live seminar. Class materials are provided in Adobe® Acrobat®  PDF file format, and can be viewed on-line or printed out. A printed copy of slide handouts are useful to have for taking notes while viewing a session. A sound card, speakers and/or headphones are required to listen to the seminar slide show audio track.  

Disc Index

  1. Hydrology

  2. Hydraulics

  3. Model Review

  4. Project Applications

  5. GIS for Engineers

  6. NPDES Stormwater Quality Issues


6 Disc Course Overview (each disc can be purchased separately) 

Disc 1 - Hydrology (3 sessions)

 

Hydrology I

This session provides an explanation of the water cycle and discusses the methods used to quantify runoff from an area using the SCS and triangular hydrograph methods.  Much more detail will be presented on the Rational Method, Site Runoff Curves and Discharge Equations.

Runoff calculation workshops using each of the three methods discussed in this session are provided along with Excel spread sheets that automate the calculations described in the workshops. This session also includes a brief discussion on the use of HEC-HMS and HEC-1, and points out the differences between them and explains how they should not be used as a “black box.”

  • Hydrologic Cycle

  • H&H Terminology - General Concepts

  • Hydrology I - Runoff Methods

  • Introduction to HEC-HMS and HEC-1

Hydrology II

The rainfall section will discuss the history and utilization of TP-40. A workshop assignment covering preparing intensity-duration-frequency curves (IDF curves) for a sample city using TP-40 data is included.

Rainfall distribution used in HEC-1 models is introduced and discussed in this session, along with how the rainfall distribution was developed and how it changes in different parts of the County.

The rainfall losses section concentrates on the basic ideas of accounting for losses.  The discussion focuses on the three loss rate methods used in Harris County, Texas, the exponential loss rate, initial/uniform loss rate and Green-Ampt method. Kinds of loss rates to expect in Harris County are provided taking into account soils, topography and level of development.

The stream routing section begins with focusing on the theory of hydrologic and hydraulic flood routing. An explanation of the differences in these two broad categories is provided.  Several common methods of stream routing will be presented including Muskingum, Muskingum-Cunge, Kinematic Wave and Straddle-Stagger.

  • Rainfall

  • Losses

  • Stream Routing

Hydrology III

This session focuses on developing runoff hydrographs starting with the Malcolm Small Watershed method.  Several handouts are provided that illustrate the implementation of this method.  The limitations and purpose of the method is also discussed. Workshops involving calculations associated with this method are provided.

The theory of unit hydrographs is discussed.  The SCS, Snyder and Clark methods of calculating unit hydrographs will be presented.  In addition the kinematic wave model for a conceptual watershed response is discussed.

  • Malcolm Small Watershed Method

  • Rainfall/Runoff Transformations

o         Unit Hydrograph Methods

o         Distributed Runoff Methods

  • Clark Unit Hydrograph Method


Disc 2 - Hydraulics (3 sessions)

 

Hydraulics I

This session covers the basic theory behind calculating water surface profiles for gradually varied steady flow, energy losses and how to account for them, and Manning’s equation and how it is used to account for friction losses.  Handouts are provided that aid in determining values for the Manning’s “n” coefficient.

The standard and direct step methods for computing water surface profiles are introduced along with examples of the proper use of each method. A workshop is provided that requires solving water surface elevations using each method.

Flow regimes are discussed along with the concept of critical depth, hydraulic jumps and backwater curves. Differences in sub-critical and super-critical flow are explained and when to expect each type of flow and what causes them to occur. 

The concept of ineffective flow areas and expansion and contraction coefficients is presented.  Their application to channels with and without structures is discussed.

  • Open Channel Flow

  • Flow Regimes and Flow States

  • Water Surface Profile Calculations

  • Open Channel Design

  • Ineffective Flow Areas (HEC-RAS preview)

Hydraulics II

This session includes a discussion of floodplains and floodways.  The concept of equal loss of conveyance due to floodplain encroachment and procedures used to define floodways.

A brief overview of the NFIP requirements for map change requests is provided.  Emphasis is given to circumstances which require map change submittals and procedures needed for various circumstances.

Information on the Floodplain Managers Certification (CFM) process is also provided in this session for those wanting to expand their expertise in the area of floodplain management.

Four case studies are provided to illustrate the information covered in this session.

  • Floodplains

  • Floodways

  • National Flood Insurance Program

o         Flood Insurance Rate Maps

o         Map Change Requests

  • Floodplain Manager Certification

  •  4 Case Studies

Hydraulics III

This session focuses on hydraulic structures.  The main categories discussed are culverts, bridges, weirs and energy dissipaters.

The theory of flow through culverts and bridges are illustrated with examples from the HEC-RAS hydraulic reference manual and TxDOT Hydraulic Design Manual.  In addition to flow characteristics through culverts and bridges, energy losses associated with these structures are reviewed along with a brief overview of bridge pier scour.

Flow over weirs is described along with a discussion about the different type of weirs, the equations used to calculate flow rates across them, the use of weirs as transition and flow control structures, along with a complete design example for the students.

Workshops for calculating inlet and outlet control flow through culverts for a variety of flow conditions is included along with additional documentation for bridge and culvert hydraulics.

  • Bridge Hydraulics

  • Bridge Scour

  • Culvert Hydraulics

  • Other Hydraulic Structures

o         Spillways

o         Weirs

o         Drop Structures

o         Energy Dissipaters


Disc 3 – Model Review (2 sessions)

These two sessions discuss the common errors that occur when running the HEC-HMS and HEC-RAS models. They are presented from the perspective of the reviewer and identify key modeling issues and parameters that warrant the attention of a plan/analysis reviewer. A list of common mistakes to look for when entering data and reviewing output, is provided for both models.

The goal of theses two sessions is to provide an awareness not only for the reviewer, for what to look for when a model is submitted, but also for the submitter so the review process will go as smooth as possible.

HEC-HMS Model Review

The input review portion of this session covers entering the data correctly into a model, basin models, meteorological models, control specifications, and existing vs. proposed conditions.

Making sense of the results is one of the topics discussed in the output review along with hydrographs, development without mitigation, channel modifications, detention mitigations and impact analysis. 

  • Input review

o         Correctly inserting the data into the model

o         Basin model

o         Meteorological model

o         Control specifications

o         Existing vs. proposed conditions

  • Output review

o         Making sense of the results

o         Hydrographs

o         Development without mitigation

o         Channel modifications

o         Detention mitigation

o         Impact analysis

HEC-RAS Model Review

This session covers the preliminary actions required for a HEC-RAS model. The HEC-RAS data checking feature and output options are explained in detail. The instructor stresses the importance of reviewing errors, warnings, notes and checking flowrates, structure crossings, boundary conditions, coefficients, and cross sections.

  • Preliminary Actions

  • Built in Data Checking by HEC-RAS

  • Check Flowrates

  • Review Output

  • View Errors, Warnings and Notes

  • Check Structure Crossings

  • Check Boundary Conditions

  • Check Coefficients

  • Check Cross Sections

 

 

Additional HEC-HMS & HEC-RAS resource materials that can be purchased from Dodson...


Disc 4 – Project Applications (3 sessions)

 

Impact Analysis

This session focuses on common tasks of hydrologic impacts analysis.  Examples of impacts and information on how to mitigate them are provided. Loss of floodplain storage and increases in discharge due to new development and/or decreases in time of concentration are addressed.

The use of detention ponds as a mitigation measure is discussed along with a demonstration of how detention changes the shape of a runoff hydrograph and the effects of detention downstream.  Also addressed is how the changes in a watershed (such as channelization and development) change the timing of runoff hydrographs. 

  • Introduction to Impact Analyses

  • How to Perform an Impact Analysis

  • Impact Mitigation

  • Detention Basins

  • Flood Plain Storage

  • Conveyance

Capstone Project

This session explores the various aspects of a typical drainage project. Developing a drainage plan, analyzing  existing and proposed conditions using HEC-HMS. Performing detention analysis and design, and studying downstream impacts. Modeling channel extension design and downstream impacts using HEC-RAS. Coordination with developer, review agencies, land planner, surveyor, and finally creating the report.

  • Refine H&H critical thinking skills

  • “day in the life” of a consulting engineer

o         typical drainage project

  • Data Collection & Review

  • Drainage Plan

  • Hydrology

o         existing conditions

o         proposed conditions

o         HEC-HMS

  • Detention Analysis

o         detention design

o         HEC-HMS

o         Downstream impacts

  • Hydraulics

o         design channel extension

o         downstream impacts

  • Client Coordination

o         developer

o         review agencies

o         land planner, surveyor, etc.

  • Report

Houston Flood Damage Reduction Feasibility Study

Dodson & Associates and Dr. Phil Bedient (review consultant), prepared a feasibility-level study to determine whether a single solution could be found to address the flooding problems in Harris County, Texas. The study assumed the flooding in Harris County generally begins at about a 10% probability (10-year) flood level. The objective of the study was to identify alternatives which would reduce 1% probability (100-year) flood levels down to 10% levels. This session compares data from a major flood that occurred in 1935 with data from more current storm events to provide an awareness of the flood prevention improvements that have been made over the years.


Disc 5 – GIS for Engineers featuring HEC-GeoHMS and HEC-GeoRAS

This disc begins with an overview of the use of GIS in hydrologic and hydraulic analysis. Advantages in terms of labor efficiency, data management, and reduction of manual errors are discussed. Limitations and possible complications associated with utilization of this technology are addressed.

Demos are provided of two common GIS-to-analysis linking tools for hydrologic and hydraulic analysis (HEC-GeoHMS and HEC-GeoRAS).  These tools were written to support the widely used ArcView GIS software and they provide a good example of current technology.  Examples on how HEC-GeoHMS and HEC-GeoRAS can be used to develop preliminary HEC-HMS and HEC-RAS models and map floodplains are included.

This disc also includes a discussion of ESRI GIS products and describes some of the recent technological developments (ArcGIS, ArcHydro, etc.)

  • Purpose of Session

o         To introduce HEC-GeoHMS & HEC-GeoRAS

o         To review a case study application, and

o         To summarize current practical capabilities.

  • Session Outline

o         Overview

o         Advantages of GIS Applications

o         Limitations of GIS Applications

o         HEC-GeoHMS Demonstration

o         HEC-GeoRAS Demonstration

o         Recent Developments


Disc 6 – NPDES Stormwater Quality Issues

This session familiarize the participants with issues surrounding the National Pollutant Discharge Elimination System (NPDES) and how those issues affect municipal projects as well as the review of private projects. 

The first section of the session details the history of the NPDES program at the federal and state levels and how the program is now enforced at the local level.  This section includes common definitions of NPDES terms and explanation of how the program is supposed to work.

The second section details the conditions of the permit that applies to Harris County, Texas (including the City of Houston, Harris County Flood Control District, and TxDOT) and how they affect municipal projects and the review of private projects.

The third section details common issues that arise with compliance with NPDES permits and how to avoid them.  This section includes preparing Storm Water Pollution Prevention Plans, actions during construction of projects, post-construction practices to reduce pollution, and reporting and recordkeeping requirements.

  • Overview of the NPDES Program

o         Clean Water Act, Water Quality Act, Total Measurable Daily Loads (TMDLs)

o         Common Definitions

  • Enforcement of the NPDES Program

o         State/EPA Authority

o         Local Enforcement

  • Local Storm Water Management Planning (Texas)

o         Joint Task Force (JTF) SWMP Programs

o         Storm Water Quality Management Plans

  • Program Areas and Permits (Texas)

o         Municipal Permits and Storm Water Plans

  • Program Areas and Permits (Texas)

o         Construction Site Permits and SWPPPs

o         Industrial Permits and SWPPPs

  • Stormwater Pollution Prevention on Construction Sites (video provided by Wal-Mart Stores, Inc.)

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