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Modified-Puls Routing Validation

Source: vignettes/validation-mod_puls_routing.Rmd
validation-mod_puls_routing.Rmd

Purpose

Validate that mod_puls_routing() produces results consistent with HEC-HMS Modified Puls routing for a benchmark dataset at Cherry Cricket Dam. The comparison benchmark uses an identical reservoir model, inflow hydrograph, and initial condition routed independently in HEC-HMS.

Modified Puls Routing

The Modified Puls routing method, also known as storage routing or level-pool routing, is based upon a finite difference approximation of the continuity equation, coupled with an empirical representation of the momentum equation (Chow, 1964; Henderson, 1966; HEC, 2025). The full derivation of the Mod-Puls routing equation from the continuity equation can be found in the rfaR Reference Manual.

Mod-Puls routing uses the known inflow, outflow, and storage at time t-1 and the known inflow at time t to estimate the the storage indicator at time t. The storage indicator uses the stage-storage-discharge relationship (your_res_model) to determine the outflow at time t.

SIt=It−1+It2+(St−1Δt−Ot−12)SI_t = \frac{I_{t-1} + I_t}{2} + \left(\frac{S_{t-1}}{\Delta t} - \frac{O_{t-1}}{2}\right)

Test 

cc_routing <- mod_puls_routing(resmodel_df = cc_resmodel,
                               inflow_df = cc_inflowhydro,
                               initial_elev = cc_init_elev,
                               full_results = TRUE)

cc_diff_elev <- cc_routing$elevation_ft - cc_hms_results$elevation_ft
cc_diff_outflow <- cc_routing$outflow_cfs - cc_hms_results$outflow_cfs

cc_max_diff_elev <- max(abs(cc_diff_elev))
cc_max_diff_outflow <- max(abs(cc_diff_outflow))
Cherry Creek Dam Routing Comparison
Metric rfaR HEC-HMS
Peak Elevation (ft) 5572.943 5572.943
Peak Outflow (cfs) 1617.820 1617.820
Max Abs Diff Elevation (ft) 0.000 NA
Max Abs Diff Outflow (cfs) 0.000 NA

Acceptance Criterion

Maximum absolute difference must be less than 0.1 ft for elevation and 1.0 cfs for outflow.

Metric Value Tolerance
Max Abs Diff Elevation 0 ft 0.1 ft
Max Abs Diff Outflow 0 cfs 1.0 cfs
Result (Elevation) PASS
Result (Outflow) PASS

Summary

Test Dam Variable Result
1a Cherry Cricket Elevation PASS
1b Cherry Cricket Outflow PASS

References

U.S. Army Corps of Engineers, Hydrologic Engineering Center. (n.d.). Modified Puls Model. HEC-HMS Technical Reference Manual. Retrieved December 18, 2025, from https://www.hec.usace.army.mil/confluence/hmsdocs/hmstrm/channel-flow/modified-puls-model