This module covers the primary tools we use to assist us in understanding and evaluating stream systems. The module includes the following topics: STREAM Spreadsheet Tools, The Reference Reach Tool, The Contrasting Channel Tool, U.S.Geological Survey (USGS) Online Tools, and Flow Routing Tools.
The tools provided in Module 3 primarily are diagnostic and educational in nature. They will not provide sufficient information to develop detailed engineering designs.
The tools can be used for any educational or research purpose provided the source of the tool is cited and the copyright privileges of author(s) is(are) not violated. Modification, redistribution or, including inclusion of any part of the tool in user interfaces or manuals, is strictly prohibited. Please see the Credits section for further guidelines on material usage.
The STREAM spreadsheet tools were developed by and, in some cases are copyrighted by, Dan Mecklenburg of the Ohio Department of Natural Resources (ODNR). Several of the spreadsheets incorporate ideas of Andy Ward from The Ohio State University (OSU).
The expectation is that: (1) the spreadsheets will be used to aid in the diagnosis of fluvial processes in wadable streams; and (2) the user(s) of these tools have adequate knowledge of hydrology, hydraulics, and geomorphology.
In the Resource Center, the spreadsheet tools are arranged based on whether they describe Channel Form or Channel Process. The tools provided in each folder are:
Each tool has its own folder. In each folder, you will find the Microsoft Excel-based spreadsheet tool, an informational fact sheet on how to use the tool and, in some cases, an example other supporting materials to aid your understanding of the tool. A detailed description of the Lane Balance tool is provided in Module 2.
Updated versions of the spreadsheets and additional tools are available in the Resource Center and the ODNR Division of Soil & Water Stream Morphology website : Stream Morphology.
Channel form is something we can look at and quantify. Making measurements on channel form is the most illuminating single step in understanding that system. Recommended details on how to conduct a channel geomorphic survey are presented in Module 1 Part 3: How to Measure Stream Features.
The main purpose of the Reference Reach Microsoft Excel-based spreadsheet tool is to aid in the analysis of geomorphology and hydraulic data that are obtained by making measurements along a reach of a wadable channel system.
The channel system can be natural, modified, or constructed and does not necessarily need to be a “reference” reach.
The spreadsheet must be populated with measured data and will be the most useful when data collection includes measurements on distinct bankfull fluvial features. Details on how to use the spreadsheet are described in the following video
The main benefits in using the tool are the large amount of time it can save in organizing field data, performing hydraulics calculations, and providing useful graphical and tabular outputs.
An example of graphical output includes a measured cross-section on Union Branch in southeastern OhioThe blue line is at the elevation of a small bankfull feature. The thin dashed brown line is at a low bank height that might have been the historic bankfull elevation. The red line is the Rosgen floodprone elevation associated with the blue bankfull line.
Tabular output associated with the cross-section data for Union Branch provides a wealth of information.
From this table, we can concisely describe the bankfull channel form:
cross-sectional area is 24.1 ft2
width is 21.3 ft
mean depth is 1.1 ft
mean velocity is 4.1 ft/s
discharge is 99.1 cfs
unit stream power is 2.7 lb/f
Manning’s n was automatically calculated from bed material data.The bed material data report a threshold grain size of 29 mm that is similar to the d50 of 28 mm.
From the profile we can see that there are 5 to 6 riffles and pools. Channel slope was automatically calculated from the profile.
The pattern encompasses 4 bends and has a sinuosity of 1.9. Riffles and pools are spaced about 4 bankfull channel widths apart. The pools are primarily on the bends and the riffles are at the cross-over point between bends.
Based on analysis of measured data of channel form, and visual observations, it appears that this stream is a slightly incised system with good connectivity to an active floodplain.
It is either in dynamic equilibrium or close to an equilibrium state. It can be classified as a Rosgen Type C4 stream.
The Reference Reach spreadsheet tool, a fact sheet on using the tool, and the Union Branch example can be downloaded in the Resource Center.
Channel processes are, to some extent, influenced by all the factors that have an impact on the hydrologic cycle (see Module 1 Part 1).
Knowledge of both channel form and channel process can aid us in determining the equilibrium state of a stream system (see Module 2 ) and also help to guide our engineering designs to re-establish dynamic equilibrium.
The main purpose of the Contrasting Channel Microsoft Excel-based spreadsheet tool is to evaluate inset channels and benches in agricultural ditches and to obtain a conceptual geometry for a two-stage channel system. It might also be useful where the focus of a project is to enhance floodplain connectivity or the size of the floodplain.
Estimated or predicted channel geometry can be adjusted to approximate a measured geometry, aggradation can be considered, and different bench (i.e. small floodplain) width ratios can be considered. Details on how to use the tool are provided in.
The tool sizes a two-stage channel system based on regional curves, hydrology, and sediment transport. Other important inputs are the bed slope, vegetation information, and the measured average particle size, or d50.
The main benefits of the Contrasting Channel tool are best illustrated by considering the same Union Branch example as in Module 3Part 3:
Based on an analysis of six measured cross-sections along a 433-foot long reach, Union Branch in southeast Ohiohas a bankfull cross-sectional area, width, and a mean depth of 21.0 ft2, 16.7 ft, and 1.3 ft, respectively. Bankfull mean velocity and discharge are 4.4 ft/s and 92.1 cfs, respectively. Bed slope is 0.93%, the d50 of the bed material is 28 mm, and the drainage area is 0.75 square miles.
Channels that form by fluvial processes are used as the baseline from which a new channel can be sized and proportioned.
Collectively, information on the geometry of these channels in a watershed or region as a function of drainage area is called a regional curve. The USGS regional curves for Ohio Region A are representative of this watershed.
Regional curve data for the Regional Geometry worksheet can be generated either by the user’s method of preference or by using default methods that are incorporated in the spreadsheet. Users can use pre-loaded regional curves or input their own from measured channel cross-section data.
The Hydrology worksheet requires knowledge of the 2-, 5-, 10-, 25-, 50-, and 100-year recurrence interval discharges.
The USGS rural and urban peak discharge methods for Ohio are the default methods incorporated into the spreadsheet.
Alternatively, the USGS StreamStats method (see Module 3, Part 6), available for many states, provides a convenient and useful approach for determining discharge versus recurrence interval relationships that can then be entered into the spreadsheet.
A discharge versus recurrence interval relationship was obtained by selecting the USGS Rural Equation for Ohio Region A (please note that Ohio Region A for the regional curves and for hydrology are not identical). For this example, the discharge relationships were not calibrated with measured gage data.
The Contrast worksheet provides the main outputs. A single channel can be evaluated or a comparison can be made between two channels.
Bankfull geometry estimated by the regional curves can be adjusted to approximate the measured geometry, aggradation can be considered, and different bench (small floodplain) width ratios can be considered.
It is important to enter the bed slope, vegetation information, and the measured d50. The vegetation information is used to estimate Manning’s n.
In the Union Branch example, we compare to channel types (A and B) with similar main channel geometries but different floodplain widths. Bankfull dimensions are very similar to those estimated by the regional curves.
The conceptual geometries in columns A and B were obtained by adjusting the channel size ratio and the width to depth ratio.
The main difference between A and B is that for geometry A, a floodplain ratio (flooded width divided by bankfull width) of 10 was compared to the existing ratio of about 2 for geometry B.
Note that in the figure, the spreadsheet has re-scaled geometry A because of the larger floodplain. The main channel has the same dimensions as geometry B.
The stages of different recurrence interval discharges are plotted in.
The recurrence interval of the bankfull discharge is a little larger than 1.6 years and has not changed by making the floodplain larger. However, the stage for the 50-year event is about 1 foot lower for geometry B with the larger floodplain.
One of the main benefits of the spreadsheet is that it considers sediment transport. The dashed lines inrepresent the bankfull stage based on a theoretical estimate of effective discharge.
The approach usually predicts an elevation slightly higher than measured elevations.
Geometry A, with the proposed wider floodplain, has good agreement between the current bankfull elevation and the theoretical estimate. Geometry B, with existing floodplain width, has much poorer agreement, and the results suggest that it lacks adequate floodplain.
The theoretical effective discharge is determined based on sediment transport associated with events of different magnitude and the number of times these events might occur over a long period of time such as 100 years.
The approach included in the tool predicts a somewhat larger recurrence interval than actually occurs. It can be seen that the larger floodplain has reduced the impact of the larger events and lowered the bedload transport potential by nearly 40%.
The Contrasting Channel spreadsheet tool, a fact sheet on using the tool, and an example can be downloaded in the Resource Center.
Velocity and discharge in a channel are based on the hydraulics of that channel.
To determine discharge in a channel, we must make measurements of the channel geometry, bed material and bed slope. Often, there are occasions when we need to estimate discharge in a channel that has not yet been constructed.
Here, we introduce a method that commonly is used to calculate velocity and discharge and present a simple Microsoft Excel spreadsheet tool for performing these calculations. More information on determining discharge in a stream is available in the Resource Center (Fact sheet AEX-445-04).
The four general approaches to determining discharge in a channel are:
Calculate discharge based on the hydraulics of the channel.
Measure the velocity of the flow in a channel.
Calculate runoff from a storm event.
Use a gage that measures changes in flow stage and a previously determined relationship between stage and discharge.
Discharge is calculated by knowing the cross-sectional area of the stream and the average velocity of the flowing water.
This is also called the general flow equation or continuity equation:
q = v1a1 = v2a2
where; q is the discharge (ft3/sec), a1 and a2 are the cross-sectional area of the stream (ft2) at upstream and downstream of a short reach and v1 and v2 are the average velocity of flowing water (ft/sec) at the two locations. Upper case letters are also commonly used for these variables.
The discharge will only remain constant if there is no loss or addition of water between the two locations.
Determining the average velocity is not simple as flow in the channel can have many forms. Often it is turbulent in places and very tranquil in other locations.
Some of the flow might actually move in an upstream direction, while at other times or other locations the flow might flow over natural or constructed structures such as beaver dams and weirs.
If the flow is fairly uniform and not very turbulent, the average velocity can be estimated by Manning's equation:
Where V is the average velocity (ft/s), S is the slope of the channel bed (ft/ft), R is the hydraulic radius of the channel (ft), and n is Manning’s roughness coefficient.
The hydraulic radius of the channel, R, is the cross-sectional area of the flow, A, divided by the wetted perimeter of the channel cross-section, P.
If metric units are used, the term 1.49 is set to 1.
In addition to not being able to account for the multitude of flow conditions that might occur in a channel, the main source of uncertainty in this equation is that Manning’s n cannot be easily determined from measurements.
Normally, Manning’s n is estimated based on published values that are associated with general descriptions of the flow conditions. Typical values of Manning’s n are shown in.
When there is out of bank flow onto a floodplain, there is lateral flow both onto the floodplain and then back into the main channel.
Also, there are often large differences in roughness of the floodplain on either of the banks and the main channel.
Errors of 50+% are probable. When there is out of bank flow onto a floodplain the uncertainty in the discharge estimate will increase.
For these conditions there is lateral flow both onto the floodplain and then back into the main channel.
Also, there are often large differences in roughness of the floodplain on either of the banks and the main channel.
Many strategies have been developed to use Manning’s equation in compound channels (channels with multiple flow stages such as a main channel and a floodplain).
The Manning’s spreadsheet tool provides results for three different strategies. These tools can be downloaded in the Resource Center.
Manning’s Equation Examples
The following example uses the spreadsheet tool to calculate velocity and discharge in a trapezoidal channel with a mean depth of 1.0 m and a bed width of 10 m.
The side slopes of the channel are 2:1 (horizontal to vertical). The bed slope is 0.005 m/m.
The channel is straight and has no deep pools. A Manning’s n of 0.03 was obtained from the Manning’s n table.
The solution is summarized in.
In the second example, we demonstrate the calculations used in the spreadsheet tool to determine velocity and discharge in a channel with a mean bankfull depth of 1.5 ft and a bankfull width of 20 ft.
The bed slope is 0.002 ft/ft. The channel has a gravel bed with a few boulders. A Manning’s n of 0.04 was obtained from the Manning’s n table.
The solution and associated calculations are summarized in.
The USGS National Water Information System (NWIS) provides current and historic water data for the United States.
The NWIS homepage has a link to a tutorial on how to use the NWIS Web Interface. Much of the information presented here was obtained from the NWIS website.
Online access to the data is currently organized as follows:
Real-time data:Current-conditions data transmitted from selected surface-water, groundwater, and water quality sites.
Site Information: Description of sites having water data.
Surface water: Water flow and levels in streams, lakes, and springs.
Groundwater: Water levels in wells.
Water quality: Chemical and physical data for streams, lakes, springs, and wells.
Mapper: Map of all sites with links to all available water data for individual sites.
Interactive maps are available for the nationand for each state.The colored dots on the maps depict streamflow conditions as a percentile, which is computed from the period of record for the current day of the year.
Real-time data typically are recorded at 15- to 60-minute intervals, stored on-site, and then transmitted to USGS offices every 1 to 4 hours depending on the data relay technique used.
Data from real-time sites are relayed to USGS offices via satellite, telephone, and /or radio telemetry and are available for viewing within minutes of arrival.
The real-time data are particularly useful in determining if flow conditions are suitable for field work.
Plots and tabulated information on gage heightand dischargeoften are available for the current condition and the prior 1 to 120 days at real-time gages.
Site information includes the drainage area, latitude and longitude, and map information.
The most useful surface water data probably will be the historic annual peak streamflows
Tab-separated files can be downloaded and then imported into spreadsheets for analysis.
We often use this data to obtain a discharge versus recurrence interval relationshipthat then is used to calibrate a hydrology model.
Procedures for determining discharge versus recurrence interval relationships are presented in the OSU Extension Fact Sheet AEX-445-04 available in the Resource Center.
The HydroTool Box Microsoft Excel add-in, available in the Resource Center, is a useful time saving tool for obtaining a discharge versus recurrence interval relationship from an annual peaks series of discharge data.
A time series of daily flows also can be obtained for gages in the NWIS database
Daily flow data are useful in determining the annual frequency of different magnitude discharges.
A useful spreadsheet tool for use with USGS daily flow data has been developed by the Office of Water Quality for the Indiana Department of Environmental Management and is available in the Resource Center.
StreamStats is a Web-based Geographic Information System (GIS) that provides users with access to an assortment of analytical tools that are useful for water-resources planning and management, and for engineering design applications, such as the design of bridges.
StreamStats allows users to easily obtain streamflow statistics, drainage basin characteristics, and other information for user-selected sites on streams.
StreamStats users can choose locations of interest from an interactive map.
If a user selects the location of a USGS data-collection station, the user will be provided with a list of previously published information for the station.
If a user selects a location where no data are available (an ungaged site), StreamStats will delineate the drainage-basin boundary, measure basin characteristics, and estimate streamflow statistics for the site. These estimates assume natural flow conditions at the site.
The introductory pages explain any unique functionality available for the state of interest and provide citations to reports that document methods implemented for that state.
Examples of some of the StreamStats outputs are presented for Klase Ditch, which is a tributary of Loramie Creek in western Ohio.
In this case, the site of interest was found by zooming in on an interactive state map of Ohio; however, latitudes and longitudes, a place name, or a reach code could have been entered.
Once zoomed in to a scale of 1:24000, or less, the watershed outlet was selected and the delineation tool button was selected to delineate the watershed.
Basin characteristics such as drainage area, 10-85 bed slope, percent forest, mean annual precipitation, and more, can be computed.
In this example, the watershed area is 3.22 square miles and the watershed has less than 5% forest cover.
Peak streamflow statistics are provided in a tabular “report” format.
The 2-year recurrence interval peak flow (PK2), for example, is 244 cfs and the prediction error is 37%.
The 90% prediction interval is 127 to 469 cfs. This may seem large but is typical, or better, than un-calibrated predictions from hydrology models.
By going to the USGS NWIS website (see Module 3 Part 5), data for the USGS gage on Loramie Creek could be obtained and then used to calibrate the discharge versus recurrence interval results to this smaller, ungaged site.
Procedures for calibrating USGS gage data are provided in the OSU Extension Fact Sheet AEX-445-04 available in the Resource Center.
Much of the information presented here was obtained from or is based on the extensive materials provided at the following website (http://www.hec.usace.army.mil/).
The Hydrologic Engineering Center (HEC), an organization within the Institute for Water Resources, is the designated Center of Expertise for the US Army Corps of Engineers in the technical areas of surface and groundwater hydrology, river hydraulics and sediment transport, hydrologic statistics and risk analysis, reservoir system analysis, planning analysis, real-time water control management and a number of other closely associated technical subjects.
The primary goal of the HEC is to support the nation in its water resources management responsibilities by increasing the Corps’ technical capability in hydrologic engineering and water resources planning and management.
An additional goal is to provide leadership in improving the state-of-the-art hydrologic engineering and analytical methods for water resources planning.
The HEC freely provides a suite of hydrologic and hydraulic routing software that are widely used throughout the nation and the world.
The two most commonly used programs in stream, ditch, and channel system projects are HEC-RAS and HEC GeoRAS.
HEC-RAS is used to perform one-dimensional steady flow, unsteady flow, sediment transport/mobile bed computations, and water temperature modeling.
The HEC-RAS system contains four one-dimensional river analysis components for: (1) steady flow water surface profile computations; (2) unsteady flow simulation; (3) movable boundary sediment transport computations; and (4) water quality analysis.
A key element is that all four components use a common geometric data representation and common geometric and hydraulic computation routines.
In addition to the four river analysis components, the system contains several hydraulic design features that can be invoked once basic water surface profiles are computed.
The steady flowcomponent of the modeling system is intended for calculating water surface profiles for steady, gradually-varied flow. The system can handle a full network of channels, a dendritic system, or a single river reach.
The steady flow component is capable of modeling subcritical, supercritical, and mixed flow regime water surface profiles.
The steady flow system is designed for application in floodplain management and flood insurance studies to evaluate floodway encroachments. Effects of various obstructions such as bridges, culverts, weirs, and structures in the floodplain may be considered in the computations. Also, capabilities are available for assessing the change in water surface profiles due to channel improvements and levees.
The unsteady flow component of the HEC-RAS modeling system is capable of simulating one-dimensional unsteady flow through a full network of open channels.
It was developed primarily for subcritical flow regime calculations.
The model can now perform mixed flow regime (subcritical, supercritical, hydraulic jumps, and draw downs) calculations in the unsteady flow computations module.
Hydraulic calculations for cross-sections, bridges, culverts, and other hydraulic structures that were developed for the steady flow component are incorporated into the unsteady flow module.
The sediment trans port component of the modeling system is intended for the simulation of one-dimensional sediment transport/movable boundary calculations resulting from scour and deposition over moderate time periods (typically years, although applications for single flood events are possible).
The model is designed to simulate long-term trends of scour and deposition in a stream channel that might result from modifying the frequency and duration of water discharge and stage, or from modifying the channel geometry.
The model can be used to evaluate deposition in reservoirs, design channel contractions required to maintain navigation depths, predict the influence of dredging on the rate of deposition, estimate maximum possible scour during large flood events, and evaluate sedimentation in fixed channels.
Sediment transport potential is computed by grain size fraction, thereby allowing the simulation of hydraulic sorting and armoring.
Major features include the ability to model a full network of streams, channel dredging, various levee and encroachment alternatives, and the use of several different equations for the computation of sediment transport.
The water quality component of the modeling system is intended to allow the user to perform riverine water quality analyses. An advection-dispersion module is included in HEC-RAS version 3.1 that adds the capability to model water temperature.
Transport and fate of a limited set of water quality constituents, including dissolved nitrogen (NO3-N, NO2-N, NH4-N, and Org-N); dissolved phosphorus (PO4-P and Org-P); algae; dissolved oxygen (DO); carbonaceous biological oxygen demand (CBOD), also is available.
HEC-RAS has the capability to perform inundation mapping of water surface profile results directly from the model.Using the HEC-RAS geometry and computed water surface profiles, inundation depth and floodplain boundary datasets are created through the RAS Mapper.
Additional geospatial data can be generated for analysis of velocity, shear stress, stream power, ice thickness, and floodway encroachment data.
HEC-GeoRAS is a set of procedures, tools, and utilities for processing geospatial data in ArcGIS using a graphical user interface (GUI).
The interface allows the preparation of geometric data for import into HEC-RAS and processes simulation results exported from HEC-RAS.
To create the import file, the user must have an existing digital terrain model (DTM) of the river system in the ArcInfo TIN format.
Water surface profile and velocity data exported from HEC-RAS simulations may be processed by HEC-GeoRAS for geographic information systems (GIS) analysis for floodplain mapping, flood damage computations, ecosystem restoration, and flood warning response and preparedness.
