Guidance for Design Hydrology for Stream Restoration and Channel Stability (2017) / Chapter Skim
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Pages 14-27
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From page 14... ...
14 C h a p t e r 3 3.1 Guidance/Examples Overview The following subsections provide some guidance and step-by-step examples for several of the tools: • Subsection 3.2: Guidance for Calculating the Half-Load Discharge (Qs50) • Subsection 3.3: Examples – Subsection 3.3.1: Example 1: Projecting hydrologic changes caused by changing land use for the Fourmile Creek watershed in central Iowa (Step 1)
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Guidance/examples 15 3.2.2 Step 2: Choosing a Reference Streamflow Gage and Indexing Flow Records At locations in which streamflow gaging records are unavailable, it becomes necessary to synthesize streamflow data from another source. The research team proposes using the index flow method to transfer streamflow records from a gaged location to an ungaged location.
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16 Guidelines for Design hydrology for Stream restoration and Channel Stability 3.2.3 Step 3: Using a Hydrologic Model to Produce Streamflow Time Series from Precipitation Records Many methods and software packages exist for rainfall-runoff modeling, for an introduction, see Beven (2011)
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Guidance/examples 17 In instances where channel geometry measurements are not available, and collecting sediment transport data is cost or time prohibitive, other methods exist for estimating sediment rating curve parameters. The eRAMS platform has the functionality to provide sediment transport capacity estimates at varying discharges for either extracted or imported cross sections.
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18 Guidelines for Design hydrology for Stream restoration and Channel Stability 3.3 Examples Much of the analysis needed to determine Qs50 for a given site can be facilitated using tools built into eRAMS. These capabilities are illustrated in the following four examples.
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Guidance/examples 19 to choose and graph outputs. Outputs can also be downloaded in a variety of formats for postprocessing.
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20 Guidelines for Design hydrology for Stream restoration and Channel Stability Figure 3-3. eRAMS SWAT-DEG interface.
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Guidance/examples 21 record from a similar and nearby gage is not the best option. This leaves hydrologic modeling as the best remaining option for obtaining a streamflow series at this site.
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Figure 3-6. eRAMS SWAT-DEG inputs for Box Elder Creek, Colorado.
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Guidance/examples 23 3.3.3 Example 3: Using eRAMS to Calculate the Richards-Baker Flashiness Index of the Iowa River near Iowa City, Iowa (Step 5) After signing into eRAMS.com and starting a new "Flow Analysis" project, the user can select a streamflow gage of interest.
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24 Guidelines for Design hydrology for Stream restoration and Channel Stability Figure 3-10. eRAMS Flow Analysis Tool output screen.
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Guidance/examples 25 Hydrologic Data Daily-averaged streamflow measurements are available from the USGS beginning in 1903. Because the site is gaged, on-site historical streamflow data should be the first choice source for hydrologic data.
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26 Guidelines for Design hydrology for Stream restoration and Channel Stability In this example, a p-value of 0.05 was used to identify significant trends. Performing the Mann-Kendall test on the annual maximum flow series yields a Mann-Kendall t value of 0.108 and a p-value of 0.244.
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From page 27... ...
Guidance/examples 27 Step 4: Divide each value in the cumulative sediment transport rate column by the total cumulative sediment transport (the sum of the rates calculated in Step 2) to calculate the percentage of cumulative sediment transport associated with each flow.
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