Hydrology Help

Hydrology - a Review for Civil Engineers ^{AIA HSW}

Russell W. Faust, P.E.

This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation. PDH Center 2410 Dakota Lakes Drive Herndon, VA 20171-2995 Phone: 703-478-6833 Fax: 703-481-9535 www.PDHcenter.com An AIA/CES Registered Continuing Education Provider (#J681)

Course Introduction

This course is intended for practicing engineers, and others, who have some basic knowledge of hydrology and hydraulics. A dictionary definition of hydrology provides some idea of the breadth of this subject:

"hy·drol·o·gy
Pronunciation: hI-'drä-l&-jE
Function: noun
Etymology: New Latin hydrologia, from Latin hydr- + -logia -logy
Date: 1762
: a science dealing with the properties, distribution, and circulation of water on and below the earth's surface and in the atmosphere."

In this course, we concentrate on those aspects of hydrology of most interest to engineers. Although groundwater is part of the hydrologic cycle, it is only briefly touched upon. The precipitation-runoff process will be the main focus of this study because it makes up so much of what engineers do on a day to day basis.

If, at the end of this course, your memory of the hydrology classes you took in college is refreshed then the course’s main objective will have been met. It is hoped too, that the references and links to websites devoted to hydrology will prove helpful to you.

Learning Objective

Upon completion of this course, the student should have:

• Gained a knowledge of basic surface water hydrology;
• Refreshed his or her memory of the hydrologic cycle;
• Know how to gather and use precipitation data;
• Found useful sources of weather data and other knowledge useful to hydrologists and engineers;
• Acquired some no cost and low cost tools for calculating flows and other hydrologic phenomena; and
• Found links to other websites where hydrologic problems are discussed and shared among colleagues.

Course Limitations

Hydrologists are concerned with all parts of the hydrologic cycle. A brief course, such as this, cannot hope to cover such subjects as groundwater movement, atmospheric energy balances, tidal dynamics, evaporation / transpiration mechanics, stream restoration and the like. Each of these subjects can take up a full semester college level course.

Those who need more detailed information on these subjects will find, however, that the references and links provided at the end of this course will lead them to many useful sources.

Course Content

1. The Hydrologic Cycle

A. The Cycle and What Drives It

Figure 2-1 is a very simple representation of the hydrologic cycle. From the oceans, and other large bodies of water, moisture evaporates in to the atmosphere forming clouds. Clouds then move over the earth’s surface and drop precipitation in the form of rain and snow. Some of this water seeps into the ground and may re-emerge in the form of springs and seeps. Much runs off or is taken up by trees and plants. Engineers are most concerned with the runoff part of the cycle, although groundwater, as a source of drinking water is of interest too.

Figure 2-1 The Hydrologic Cycle

What drives the whole process, of course, is the sun. The uneven heating and cooling of the earth’s surface by the sun’s rays is the energy source; the engine of the hydrologic cycle.

Another useful way to look at the cycle is illustrated in Figure 2-2.

Figure 2 - 2 Annual Water Balance for the Mediterranean Sea

The hydrologic cycle has been around for as long as there has been an earth. Only in recent years has man’s ability to measure it been improved through some of the advances in technology cited in Section 8 below.

2. Runoff Processes and Data Sources

A. Rainfall and Snow

B. Storage

Example Basin

Location: North coast region of California

Drainage Area: 100 Acres

Impervious Area: 75 Acres C= 0.90

Pervious Area: 25 Acres C= 0.60 Tc = 30 minutes

(caclulated below)

100 Year Intensity @ 30 min. = I₁₀₀ = 1.52 in/hr

Weighted Average C = 0.83 CN on Pervious Area = 66

Hydrologic Soil Group C

Here’s a sketch of our basin.

Figure 3 – 2 Example Drainage Basin

We’ll also assume some rainfall characteristics as illustrated by the hyetographs in Figure 3 - 3.

100 Year 24 Hour Rainfall Hyetograph - Type 1A Storm

100 Year - 24 Hour Cummulative Rainfall - Type 1A Storm

Figure 3 – 3 Assumed Rainfall Characteristics

In the following sections of this course we will use this example basin to illustrate several deterministic and statistical approaches to the hydrologic analysis of this basin.

In order to touch upon the question of detention storage, we'll also assume that it would be desirable to build a regional detention basin at the downstream end of this catchment. Complete design of such a detention basin would be more complex than we can cover in the space of this brief review. A preliminary design can be completed and will help in understanding of the factors involved.

3. Deterministic Methods of Design

Deterministic methods include all those calculations which attempt to predict hydrologic quantities such as flow, velocity, time of concentration, etc. by the application of known laws of physics combined often with empircally derived constants or coefficients. Such methods try to use measurable characteristics of the watershed, such as soil type, ground cover, slope, area and so on to arrive at the desired hydrologic quantity.

A. The Rational Method

About the year 1860, Emil Kuichling, City Engineer of Rochester, New York proposed the so called "Rational Formula"; Q = CIA, for calculating the peak runoff from an urban drainage basin. He presented his ideas in a paper published in the ASCE Journals along with the data from five test basins he had monitored. His simple equation tries to model the complex series of events which take place during a storm. The method is easy to use, requires only a small amount of data and, for small watersheds, appears to give reasonable answers. It is thought by many to be conservative by overestimating the flow.

Despite it’s obvious drawbacks, the method continues to be widely used today, although sometimes it is misapplied to larger watersheds for which it has never been demonstrated to be applicable. We’ll use the method below and apply it to our 100 acre example basin.

B. TR-55 Computer Modeling

In May of 2003 the NRCS published an updated version of the software for TR-55. Called Win TR-55, it may be used in place of the tabular and graphical methods last released in 1986. Here's a brief description:

WinTR-55 is a single-event rainfall-runoff small watershed hydrologic model. The model generates hydrographs from both urban and agricultural areas and at selected points along the stream system. Hydrographs are routed downstream through channels and/or reservoirs. Multiple sub-areas can be modeled within the watershed.

To download the program and documentation got to:

http://www.wcc.nrcs.usda.gov/hydro/hydro-tools-models-wintr55.html

Win TR-55 still has similar limitations to its predecessors. The most important of these is that it still allows modeling of only the 24 hour storm duration. For other durations you'll need to find other means or programs to do the calculations.

C. Time of Concentration

There are at least seven methods in common use in the US. They include:

• Izzard's Formula
• Kerby's Equation
• Kirpich's Equation
• Kinematic Wave Equation
• Bransby Williams Equation
• Federal Aviation Agency Equation
• TR-55 Worksheet Method

The TR-55 method is shown below. It incorporates the kinematic wave equation with other methods to arrive at a total travel time.

Nearly all of the methods in use require an estimate of the time of concentration, Tc. The time necessary for runoff from the remotest point in the drainage basin to the point of interest can be estimated in a variety of ways. The one which seems to make the best sense is probably that presented in TR-55.

Here is the tabular method used by TR-55 as applied to our example watershed.

Figure 4 – 4 Time of Concentration Using TR-55

There are at least five other methods in common use. Although not presented here you can find explanations of them in References 2 and 4.

D. Limitations and Errors

Deterministic methods all require experience and judgement by the designer. The choice of "C" values, the selection of Curve Numbers, assumptions about infiltration, the choice of design storm duration, etc., etc. are all subjective at best. Two designers, working with the same basic data will almost always come up with different answers.

Some studies show discrepancies of between 30 and 50 percent in the peak flow calculated by various designers using the Rational Method.

This suggests that hydrology remains more art than science despite the many advances we’ve seen over the last two centuries in the United States. It also suggests that we should treat all the numbers generated, whatever the technique used, with great skepticism.

4. Statistical Methods

A. Gaged Streams

Fortunate indeed is the engineer who works on a project which is at or very near a stream gage. Records of stage and flow will exist for him to draw upon, analyze, and use to estimate future flood events. But stream gages are few, records are often short or incomplete, and gages are far apart. Figure 5-1 shows just one of the many types of data which may be available in your state.

Figure 5 – 1 Streamflow Data for Oregon

B. Regression Equations

In many parts of the country, hydrologists and others have developed regression equations for estimating flows on ungaged streams. Many are for undeveloped basins although some urban areas have also been analyzed in this way. Here is a set of equations developed some years ago for the north coast region of California by the USGS.

Return Period Equation

As an exercise, calculate the 10, 25, and 100 year flows for our example basin. Assume average annual precipitation is 42 inches and an altitude index of 1.0 .

You should get the following values:

We’ll use these flows below to compare them with estimates derived by other methods.

C. Adaptations for Urban Areas

As noted above, most regression equations are based on data from rural, undeveloped basins. Several investigators have modified these for urban areas. If this interests you see References 3 and 4 listed at the end of this syllabus. It is also suggested that you visit the USGS webpage and find out if someone has developed more recent equations for your area, especially if yours is an urban area where flood damage may be high creating the incentive to do such studies.

D. Limitations and Errors

Regression equations can yield estimates of peak flow but obviously provide no hydrograph information. Most are developed from gaged streams so the designer must be aware that application to an ungaged basin may not give good estimates if the ungaged basin is far from the gaged sites or differs considerably geographically or climatologically.

5.Design Storms

A. Standard Design Storms

The NRCS developed the rainfall patterns for geographic areas across the United States and simplified them into four types, I, IA, I and III. All are 24 hour duration and tend to be centrally weighted, i.e. the heaviest rainfall occurs near the middle of the duration. Figure 6-1 is reproduced from TR-55.

Corps of Engineers Standard Project Flood

Flood control projects constructed by the Corps of Engineers are sometimes evaluated with the standard project flood (SPF) (USACE, 1952). Safe and effective performance during the SPF is desirable when the project is intended to protect communities with large human populations and especially valuable property. The SPF is the result of the standard project storm (SPS) in combination with the reasonably expected operation of any existing or proposed flood control projects or other hydraulic control structures in the watershed. The SPF must also consider the antecedent soil moisture conditions likely to prevail at the beginning of a large storm event. The SPS is intended to represent the most severe combination of a rainfall depth-area-duration relationship and isohyetal pattern considered reasonably characteristic of the watershed.

Hydrologic Modeling System HEC-HMS

B. Developing Regional Design Storms

The standard design storms, of course, represent a great simplification of the wide variety of weather patterns across the country. It would be possible, to customize these rainfall patterns to suit local conditions. In some places this has been done but much more work is still needed along these lines.

C. Arbitrary Regulations and Methods

Many Cities, Counties, Flood Control Districts and other regulatory agencies have developed design standards for their local areas. These are all necessarily, to some extent arbitrary. It is simply not possible to design regulations to fit every set of facts which might arise in any given design situation.

Some are better than others, however, so be aware that as the designer you’ll want to satisfy yourself that what you’ve designed is reasonable and will work under most circumstances. The best test of any design will always be to ask yourself " what would be the consequences of failure ?"

D. Hydrographs

1. An Actual Storm Hydrograph

Both the Rational Method and modified Rational method can be illustrated using our example basin.

First, the Rational Method for the 10 year (undeveloped) 25 year and 100 year (developed) storms:

Q₁₀ = CI₁₀A

Q_{10 =} (0.60)(0.97)(100)

Q_{10 =} 58.2 cfs

Q₂₅ = (0.83)(1.11)(100)

Q₂₅ = 92.1 cfs

Q₁₀₀ = (0.83)(1.52)(100)

Q₁₀₀ = 126.2 cfs

We now think we know three flows but we have no hydrographs so routing flows through a detention basin is not possible.

To answer this difficulty many public agencies, including the Oregon Department of Transportation ( ODOT), have adopted the so called Modified Rational Method. In this method a series of hydrographs are assumed as shown in Figure 6-2.

Figure 6-2 Assumed Hydrographs

The first hydrograph is assumed to be triangular with a rise time to the peak flow equal to Tc. Then, hydrographs for a range of durations are assumed. These are trapezoidal in shape and all have the same time to peak but different base widths. In this simplified method, it is also assumed that the outflow is constant.

What we’re looking for is the hydrograph that encloses the greatest area between itself and the outflow hydrograph". This is the duration which theoretically requires the maximum volume of storage.

These calculations may be easily setup in a spreadsheet. Below is our example basin calculated using Corel Quattro Pro, Ver. 8.

Over the years, many synthetic hydrographs have been developed. What follows is a brief description of several of them. In the belief that practicing engineers need to know how to use these hydrographs, rather than how they are derived, details of the calculations are not included. References 3, 4 and 5 can provide that information, if you need it.

And finally, a screen capture of the Clark Hydrograph using SMADA.

Figure 6-5 Clark Method Hydrograph

SMADA does not calculate the Snyder hydrograph, or several others. This is partly because the Snyder method was developed for catchments in the Appalachian mountains and must be adjusted for other regions of the country. Adjustment requires comparing the shape of the calculated hydrograph to known hydrographs for the area and assigning appropriate values to coefficients used in the calculation to make both look as nearly alike as possible. Figure 6-6 does illustrate this basic shape, however.

Figure 6- 6 The Snyder Hydrograph

Flow Comparison

Pilot tests by the US Water Resources Council have shown that all the models tested are subject to errors; large errors. Most tend to overestimate flows but errors can range from 30 to 50 percent in many cases. Some of this error is due to the imprecision of the data used as input . Part of it is also a result of the fact that no model can exactly predict peak flows even if all the data is correct.

We now have several calculated flows which we can compare to see how widely they vary. Arbitrarily, we’ll use the Regional Regression Equation flows as the basis for comparison.

Method Q₁₀₀ cfs Difference %

Reg. Regression Equations 68.9 -----

Rational Method 126.1 +183

SCS 484 Hydrograph 74.1 + 7 %

Santa Barbara Urban Hydrograph 66.3 - 4 %

Clark Hydrograph 64.3 - 7%

6. Detention Storage Design by the TR-55 Method

A. Detention Storage, the General Solution

In all detention basins we are usually seeking to controls the outflow from the basin to approximate conditions before development, i.e. urbanization, occurred. Figure 7-1 represents the hydrographs for the before and after conditions. The area between the two hydrographs is the volume of storage needed. If we could know exactly what these hydrographs looked like we could theoretically design the "perfect" detention basin. We cannot know, of course, so numerous methods of approximating this required volume have been devised. One of the most common is that contained in Urban Hydrology, Technical Release No. 55, in 1986 by the Soil Conservation Service ( now known as the NRCS). TR-55 presents a simplified method for sizing detention basins and we’ll use it here for our example drainage basin .

Figure 7-1 Typical Detention Basin Hydrographs ( Ref. 3)

It is worth repeating, the area between the inflow and outflow hydrographs represents the volume of storage needed. If you memorize Figure 7-1 you’ll remember this basic principal.

The TR-55 method has six steps and is very straightforward. Using our example drainage basin, let’s suppose that the design peak inflow is 74.1 cfs as calculated using SMADA (SCS 484 Method) above. Very arbitrarily, we’ll also suppose that it is desired to reduce the peak outflow from the detention basin to the 10 year flow of 50.0 cfs (calculation not shown above). This decision is indeed arbitrary so we’ll discuss it at the end of this section again.

We now calculate the ratio of the peak outflow (Qo) to peak inflow (Qi).

Qo/Qi = 50.0 / 74.4 = 0.67

We now determine the volume of runoff in cubic feet or acre-feet. Fortunately, SMADA also does this calculation for us, or we could plot the hydrograph and planimeter the area under it to arrive at the answer. SMAD calculated 4.17 inches of runoff over our 100 acre basin. This is equal to 1,513,710 cubic feet.

TR-55 provides a graph, shown here as Figure 7-2, which allows us to calculate the ratio of the Volume of storage ( Vs ) to the Volume of runoff ( Vr ). Entering the graph along the horizontal axis at 0.67 and then extending a line to the vertical axis we arrive at a value for Vs/Vr of 0.14.

Therefore, are required storage volume is (0.14)(1,513,710 ) = 211,900 cf rounded to the nearest 100cf.

This is considerably more than the 60,000 cf calculated by the Modified Rational Method earlier.

Figure 7-2 Required Detention Storage TR-55

To complete the design we would have to do considerably more, of course. We’d need to determine the size and shape of the basin and develop the stage storage relationship. This would require that we design the outlet control structure which might be a weir, an orifice, a gate or a simple culvert. We’d also need an emergency spillway designed to allow overflow whenever the maximum probable storm occurs. Finally, we would probably want to route a range of storms through our detention basin to be certain of how it would operate under all conceivable conditions.

B. Understanding the Risks

An Implied Level of Protection

We often speak of the selected return period for design as "the 50 year flood" or "the 100 year flood." Many who hear this understand it to mean that this is a flood expected to occur once every 50 or 100 years. By speaking this way we imply a level of protection which is seldom achieved. For example, if we design for a 100 year storm event many people would believe that would mean the system should function for 100 years without ever being over capacity.

Unfortunately, this is not true. Because flood probabilities are based on historical records, their accuracy depends on the length and completeness of those records. Many reporting stations have only a few years of record so that the probabilities calculated from them are less reliable than stations with a record of 40, 50 or more years. As this is being written NOAA is updating their precipitation frequency records adding an additional 30 years of record to the data. This should improve the accuracy of the published data and make our estimates more reliable. Even so, they will remain "estimates" only. That is, they are simplified ways of stating the probability of an unpredictable event occurring.

A possibly better way of viewing these events, and speaking about them, is to refer to them by their annual probability of occurrence. The so called 100 Year storm is, by definition, the storm which has a 1 percent probability of occurring in any one year. If we want to know how frequently such a storm might occur over a longer period of time, that probability can be calculated by:

P_x = 1 - ( 1-1/N)^x

Where: P_x is the probability of occurrence in x number of years

1/N= the Probability of Occurrence in any one year

For example, if we want to calculate the probability of occurrence of the 100 year flood over 100 years the calculations would be:

P_x = 1 - ( 1-1/100)¹⁰⁰

P_x = 1 - ( 1- .01) ¹⁰⁰

P_x = 1 - ( 0.99)¹⁰⁰

P_x = 1- 0.366

P_x = 0.634

In other words, there is a 63 percent probability that the 1 Percent storm will occur one or more times over the next 100 years.

This kind of calculation can be done for any selected range of frequencies and time periods. This has been done in Figure 7-3.

Figure 7-3 Probability of the N Year Event Occurring in x Years

C. How Much Insurance Can You Afford to Buy ?

You may find it helpful to think of storm water management measures as insurance. The question for the designer then becomes, "how much protection do I need and how much can I afford ?" If your project is to design protection for the regional hospital in your area you’d probably want a very large "insurance policy" to protect this vital community resource. But, if the only thing downstream from you detention basin is a large community park a much lower level of protection can be justified.

7. New Developments and Approaches

On the horizon are many new devices for gathering and analyzing data. Among these may be included; remote sensing rain gages, radar detection, and GIS systems which can be used to calibrate mathematical models of the runoff process. Satellite imagery has become literally as regular as the Six O'clock news and has provided climatologists vast amounts of information on large weather systems. With this, predictive models can be refined and is being used increasingly to provide advance warning of truly dangerous weather.

On a theoretical level, hydrology is a little better understood than it was in Emil Kuichling’s day but much remains to be done. Using only 4 design storms for all of the United States, for example, is probably not the best we can do. With a little more work, it appears we might devise regional design storms more realistically reflecting local conditions.

Finding the optimum storm duration for design for various regions of the country would be another useful step.

Increasingly, water quality is becoming a factor for the hydrologic designer. Using treatment schemes and so called "best management practices" , BMPs will become a requirement under Federal and local regulation. This part of hydrology is truly in its infancy and much more work needs to be done before we can say we know what is "best".

8. Conclusions and Recommended References

This course can provide only a brief overview of the widely ranging study of hydrology and its related discipline, hydraulics. The references and links below have been useful to the author and are suggested to you. Visit at least a few of them and you’ll be rewarded. They will lead you to others and to a world of interesting places.

References, Software and Links

References

1. Hydrology for Engineers, Linsley, Kohler and Paulhus,Mc Graw - Hill Book Co., New York, NY

2. Stormwater Management, Quantity & Quality, Martin P. Wanielista, Ann Arbor Science, Ann Arbor, MI

3. Handbook of Hydraulics, Brater and King, Mc Graw - Hill Book Co., New York, NY

5. Urban Hydrology, TR-55, USDA, Soil Conservation Service, 1986

6. Flood Runoff Analysis, ASCE Press, New York, NY

Software

SWMM is a dynamic rainfall-runoff simulation model, primarily but not

exclusively for urban areas, for single-event or long-term (continuous)

simulation. Flow routing is performed for surface and sub-surface conveyance and groundwater systems, including the option of fully dynamic hydraulic routing in the Extran Block. Nonpoint source runoff quality and routing may also be simulated, as well as storage, treatment and other best management practices (BMPs). Version 4.3 (May 1994) contains corrections and enhancements to Version 4.20 (June 1992), including a new Transport flow divider, revised hydraulic radius calculations for natural channels in Extran and Transport (to agree with the HEC-2 method), multiple land use options in Runoff, additional sewer infiltration options, improved manipulation of long-term rainfall data (especially 15-min data), a linkage to WASP4 from Transport, additional statistical output from Runoff and many other corrections and enhancements to various program options

SMADA

The SMADA programs were written to accompany the textbook Hydrology: Water Quantity and Quality Control 2nd Edition by M.P. Wanielista, R. Kersten, and R. Eaglin. The text is available from John Wiley and Sons publishers.

A manual for the computer programs is available by sending a check or money for $95.00 (made out to R. Eaglin) to (Non-US orders should add $20 foreign shipping cost):

SMADA Manual c/o Ron Eaglin
1155 Elm Street
Oviedo, FL 32765

Support for this software is through e-mail only, questions should be sent to:eaglin@magicnet.net.

The documentation contains information on:

Using SMADA
SMADA Theory
Using TCALC
Using REGRESS
Using DISTRIB
Using EZMAT

Consulting services are available and inquiries can be made to the e-mail address shown above.

HEC-HMS

The Hydrologic Modeling System is designed to simulate the rainfall-runoff processes of dendritic watershed systems. It is designed to be applicable in a wide range of geographic area for solving the widest possible range of problems. This range includes large basin water suply (sic) and flood hydrology, and small urban or natural watershed runoff.

Haestad Methods

PondPack v7.5

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Highlights:

PondMaker Design Wizard
Pond Dimension Solver
Interconnected Ponds
Multistage Outlets
Hydrograph Methods
Full Watershed Networks

Detailed Feature List:

New! PondMaker Design Wizard
Watershed Networks and Interconnected Pond Modeling (ICPM)
Rainfall and Runoff Computations
Hydrograph Procedures
Time of Concentration
Routing
Pond Volumes
Channels
Outlet Structures
Water Quality Best Management Practices (BMPs)
Reporting and Graphing System
Requirements

StormCAD v4.1

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Highlights:

Fastest model on the market
Seamless GIS integration
Amazing ease of use
Unlimited undo/redo
Cost Analysis
Stand-Alone / AutoCAD

Detailed Feature List:

Stand-Alone Interface
AutoCAD Interface
Pipe & Gutter Networks
Pipe Hydraulics
Structure Hydraulics
Drainage Inlet Hydraulics
Built-In Hydrology
Automatic Design
Scenario Management
Flexible Tables (FlexTables™)
Data Sharing
Plan & Profile Results
Comprehensive Reporting

FlowMaster

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Interface

Analysis and Design

Reporting

Data Management

Prices

FlowMaster v6 is an efficient and powerful program for the design and analysis of pipes, ditches, open channels, weirs, orifices, and inlets. FlowMaster's "Hydraulics Toolbox" can solve or rate any unknown variable using the Manning's, Hazen-Williams', Kutter's, Darcy-Weisbach, and Colebrook-White formulas. FlowMaster's new inlet computations strictly comply with the latest FHWA Hydraulic Circular Number 22 (replacing Circular 12) and AASHTO inlet computation guidelines.

Interface:

FlowMaster's interface is simple enough to make it the easiest model you have ever used, yet so powerful that you will be solving multiple uniform flow problems simultaneously in minutes.

Create an unlimited number of worksheets to manage the data for your entire project

Metric, English, or a combination of both unit systems

Solve for any unknown - flow, slope, channel width, pipe diameter, section roughness, etc

FlowMaster has been radically improved and optimized to be faster and smoother than ever

Run under Windows 95, 98, or NT

Get free updates over the Internet via the globe button

Tabbed dialogs organize data for easy input and output

Analysis and Design:

FlowMaster will solve for any unknown variable in gutter cross sections, inlets, weirs, orifices, irregular channels, pressure pipes, or standard open channels. Create multiple design trials, calculate them all simultaneously, and compare the results in customizable tabular reports.

Model curb, grate, slot, combination, and ditch inlets using calculations based on FHWA Hydraulic Engineering Circular No. 12 and Circular No. 22 methodologies

Analyze any inlet in sag or on grade with a continuously or a locally depressed gutter

Calculate water spread and gutter depth for a gutter or pavement section

Size or evaluate flow for sharp-crested weirs, broad-crested weirs, and orifices

FlowMaster will solve for any variable, including discharge, headwater elevation, discharge coefficient and more. Even submergence (tailwater effect) in orifices and weirs is taken into account

Enter the geometry and variable roughness for your irregular sections (open or closed) to model irregular open and closed cross sections effortlessly

Compute composite roughness values for your irregular section using various methods including Lotter, Horton, Pavlovskii, or the Colebatch and Cox method, as well as the combination of Horton and Lotter that was available in the previous version

Model ditches and swales regardless of size and shape. Geometric shapes include circular, rectangular, trapezoidal, triangular, gutter, and irregular

Perform a quick check or a design on a pressure pipe by simply plugging in the known information and clicking to solve for the unknown

Reporting:

With FlowMaster's improved reporting tools you can create quick summary reports and customized tabular reports along with graphs, performance curves, and rating tables. Every report, curve, and graph is completely customizable with full copy and paste support.

Summary views and reports

Computations of ratings tables by varying one or more input variables simultaneously

Single curve plots and families of curves

Performance curve comparisons

Cross-sectional views

FlexTables to view, edit, and create custom reports for multiple worksheets

Graphing and plotting of all output including support for all color printers

Windows clipboard capabilities, such as copy and paste. FlowMaster reports, rating tables, rating curves, and cross-section plots can be incorporated into your documents with a click of your mouse

Data Management:

Use multiple worksheets within the same file to document multiple design trials, or to analyze and design multiple parts of a project without generating large numbers of confusing files.

Organize projects into one file with multiple worksheets

Organize, input, and output data in customizable FlexTables that display the selected data for multiple worksheets

Use FlexUnits to select the units you want (metric, English, or a combination of both) and display or print to any decimal precision

# of Users Price:

1 : $495.00

2 : $795.00

5 : $1,795.00

10 : $2,495.00

Contact Us:

Haestad Methods · 37 Brookside Road · Waterbury, CT 06708 · USA

Voice: +1-203-755-1666 · Fax: +1-203-597-1488 · Visit: www.civilprojects.com

Links

The Hydrology Web http://etd.pnl.gov:2080/hydroweb.html

Ten Links http:www.tenlinks.com/civil

A large reference library and many links throughout the world

NOAA

Current Precipitation Frequency Publications

NOAA Atlas 2, Precipitation Frequency Atlas of the Western United States,(1973). Generalized maps and presented for 6- and 24-hr point precipitation for the return periods of 2, 5, 10, 25, 50, and 100 years. Equations are interpolation diagrams are provided for determining values for durations less than 24 hours and for intermediate return periods. Area reduction curves for adjusting point values for areas up to 400 square miles are included. This Atlas is published in a separate volume for each of the 11 Western States. Scanned images of NOAA Atlas 2 at the Western Region Climate Center.

Volume I. Montana ($9.00)

Volume II. Wyoming ($9.00)

Volume III. Colorado (Loan copy only)

Volume IV. New Mexico ($9.00)

Volume V. Idaho ($9.00)

Volume VI. Utah ($10.00)

Volume VII. Nevada ($9.00)

Volume VIII . Arizona ($9.00)

Volume IX. Washington ($9.00)

Volume X. Oregon ($9.00)

Volume XI. California ($10.50)

All 11 Volumes ($98.00)

Technical Paper 40, Rainfall Frequency Atlas of the United States for Durations from 30 minutes to 24 Hours and Return Periods from 1 to 100 Years (1961, $15.50). Rainfall-frequency values for selected durations from 30 minutes to 24 hours and return periods of 1 to 100 years are given on a series of maps. NOTE: This publication is superseded in part by Technical Memorandum NWS Hydro 35 and NOAA Atlas 2. Technical Paper 42, Generalized Estimates of Probable Maximum Precipitation and Rainfall-Frequency Data for Puerto Rico and Virgin Islands (1961, $23.50)

Technical Paper 43, Rainfall-Frequency Atlas of the Hawaiian Islands for Areas to 200 Square Miles, Durations to 24 Hours, and Return Periods from 1 to 100 Years (1962, $15.00) Technical Paper 47, Probable Maximum Precipitation and Rainfall-Frequency Data for Alaska for Areas to 400 Square Miles, Durations to 24 Hours, and Return Periods from 1 to 100 Years (1963, $17.25)

Technical Paper 49, Two-to-Ten-Day Precipitation for Return Periods of 2 to 100 Years in the Contiguous United States (1964, $7.25) Technical Paper 52, Two-to-Ten-Day Precipitation for Return Periods of 2 to 100 Years in Alaska (1965, $7.50)

Technical Paper 53, Two-to-Ten-Day Precipitation for Return Periods of 2 to 100 Years in Puerto Rico and Virgin Islands (1965, $8.75)

Technical Memorandum NWS Hydro 35, Five to 60-minutes Precipitation Frequency for Eastern and Central United States (1977, $9.00). Precipitation-frequency values for the Central and Eastern United States for return periods from 2 to 100 years for durations of 5 minutes to 1 hour are provided in a series of maps and graphs. This material supersedes the similar material published in Technical Paper 40. Note: All Technical Papers are available only as photocopies.

The use of the word "CURRENT" is a bit of a mis-statement. Our use of the word current refers to the applicable document at this time. The reports, mainly Technical Paper 40, NOAA Atlas 2, and Technical Memorandum NWS Hydro 35, are being updated using 30 more years of data and new statistical techniques. The Semiarid Southwest precipitation frequency atlas is expected to be completed by the end of this year. The Puerto Rico and Hawaii studies are in progress. Studies for the Ohio River Basin began in 1997 and will be followed by other areas until all the "CURRENT" studies are updated.

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