(each disc can be purchased
Disc 1 - Hydrology
session provides an explanation of the water cycle and discusses the
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.
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.”
H&H Terminology - General Concepts
Hydrology I - Runoff Methods
Introduction to HEC-HMS and HEC-1
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.
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.
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.
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.
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.
of unit hydrographs is discussed. The SCS, Snyder and Clark
methods of calculating unit
will be presented. In addition the kinematic wave model for a
conceptual watershed response is discussed.
Unit Hydrograph Methods
Distributed Runoff Methods
Disc 2 - Hydraulics
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.
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.
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.
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)
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.
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.
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.
studies are provided to illustrate the information covered in this
Flood Insurance Rate Maps
Map Change Requests
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.
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.
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.
Disc 3 – Model Review
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
review portion of this session covers entering the data correctly
into a model, basin models, meteorological models, control
specifications, and existing vs. proposed conditions.
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.
Correctly inserting the data into the
Existing vs. proposed conditions
Making sense of the results
Development without mitigation
HEC-RAS Model Review
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.
Built in Data Checking by HEC-RAS
View Errors, Warnings and Notes
Check Structure Crossings
Check Boundary Conditions
Check Cross Sections
Additional HEC-HMS &
HEC-RAS resource materials that can be purchased from Dodson...
Disc 4 – Project
Applications (3 sessions)
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.
session explores the various aspects of a typical drainage project.
Developing a drainage plan, analyzing
proposed conditions using
HEC-HMS. Performing detention analysis
studying downstream impacts. Modeling channel extension
downstream impacts using
developer, review agencies,
land planner, surveyor,
finally creating the
typical drainage project
Data Collection & Review
design channel extension
land planner, surveyor, etc.
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
Disc 5 – GIS for Engineers featuring HEC-GeoHMS and HEC-GeoRAS
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.
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
also includes a discussion of ESRI GIS products and describes some
of the recent technological developments (ArcGIS, ArcHydro, etc.)
To introduce HEC-GeoHMS & HEC-GeoRAS
To review a case study application, and
To summarize current practical capabilities.
Advantages of GIS Applications
Limitations of GIS Applications
– NPDES Stormwater Quality Issues
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
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
Clean Water Act, Water Quality Act, Total Measurable
Daily Loads (TMDLs)
Joint Task Force (JTF) SWMP Programs
Storm Water Quality Management Plans
Municipal Permits and Storm Water Plans
Construction Site Permits and SWPPPs
Industrial Permits and SWPPPs