Comparison of overland flow diffusion wave model with SWMM and HEC-HMS

(Preliminary)

March 24, 2014Rosa Aguilar

Computational Hydraulics and Hydrology

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Surface RunoffWater flow that occurs when the soil is infiltrated to

full capacity and excess water from rain, meltwater, or other sources flows over the land (wikipedia).

Modeling

• Watershed runoff must be predicted to provide the information for certain activities:• Increased volume of runoff for proposed changes to land

use in a watershed.

• A model relates something unknown (the output) to something known (the input).

Modeling Systems

• Hydrologic Modeling System (HEC-HMS)• 2013

• EPA’s Storm Water Management Model (SWMM)• 2011

• Overland flow diffusion wave model• 2013

HEC-HMS

• US Army Corps of Engineers• Four versions since HEC-1 • Version 1: Graphical user interface.• Version 2: Continuous simulation.• Version 3: New computational features and graphical user

interface.• Snowmelt, evapotranspiration, infiltration, data management,

increase user efficiency.

• Version 4: New computation features.• Surface erosion and channel sediment transport• Nutrient water quality simulation

HEC-HMS

• Kinematic wave

• Lag

• Modified PuIs

• Muskingum

• Muskingum-Cunge Standard Section

• Muskingum-Cunge 8-point Section Confluence

• Bifurcation

Routing Models

EPA SWMM

• Routing models • Steady flow• Kinematic wave• Dynamic wave

EPA SWMM

• Steady Flow: Instantaneous translation of a hydrograph with no time delay or change in shape due to conduit storage.

• Kinematic Wave: Efficient but simplified approach that cannot deal with backwater effects, pressurized flow, flow reversal, and non-dendritic layouts. Numerical stability attained with moderately large time steps, on the order of 5 to 15 minutes

• Dynamic Wave: Can represent these conditions. However, the procedure requires more computation time, due to the need for smaller time steps to maintain numerical stability.

Overland flow diffusion wave model

Simulates catchment dynamics using the diffusion wave model developed by Ponce (1986). The program is a numerical model of overland flow using an open-book schematization.

• Outflow hydrograph does not vary with the choice of grid size.• Physical diffusivity of Hayami:

• Numerical diffusivity of Cunge:

• Cell Reynolds number:

Overland flow diffusion wave model

Overland flow diffusion wave model

• Diffusion wave with dynamic components• Dynamic hydraulic diffusivity:

• Numerical dispersion is minimized by setting the Courant number C equal to 1:

Fig. 1 Effect of grid resolution on the outflow hydrograph, 12-hr rainfall duration, 2 cm/hr rainfall intensity, 18-ha watershed area.

Further Studies

• Run HEC-HMS and SWMM.

• Run the runoff simulation models with the data used in Overland flow of diffusion wave model.

• Compare the results.

References

• Ponce, V.M., 1986. Diffusion Wave Modeling of Catchment Dynamics Journal of Hydraulic Engineering, 112(8). pp. 716-727.

• Wikipedia. (2014, March 23). Surface Water. Retrieved from http://en.wikipedia.org/wiki/Surface_water

• Mahomet Aquifer Consortium. (2014, March 23). MAC Educational Materials/ 2: Hydrologic Cycle. Retrieved from http://www.mahometaquiferconsortium.org/