Skip to Main Content

Hydrologic Engineering Centers River Analysis System (HEC-RAS, US Army Corps of Engineers) is a one-dimensional (1D) flow routing approach based on the St Venant/Shallow Water Equations (Horritt & Bates 2002; Pappenberger et al. 2005). It has been around in hydraulic design and engineering research for a few decades and is adopted in this study because of its well-performing theoretical basis (Horritt & Bates 2002; Drake et al. 2010; Morche et al. 2010). Based on the data collected in September 2011 and 1 m DEM data, HEC-RAS models for ten selected river sections in the Stör catchment were set up and calibrated, and during this process a combination of roughness and bed gradient calibration was involved. Due to the difficulty in determining a representative Manning's n value, our main attention was focused on roughness calibration to achieve the minimum error between real measured and modeled water surface elevations, maximum depth, hydraulic depth and mean cross-sectional velocity. Finally, the averaged errors between measured and modeled data of all the models were within ±5% (Song et al. 2014). The dataset from January 2012 was used for model validation, and the validation quality is shown in Table 2. The HEC-RAS output and field surveyed data were positively correlated in the validation model. All the correlation coefficients were higher than 0.9. This indicated reliable performance of the steady model, and provided the basis for the application of the modified Manning formula.

Table 2

Relative error of steady models

Relative error (%)Calibration
Validation
WSEMDHDMCVWSEMDHDMCV
cs7 0.31 3.37 1.01 3.75 4.43 8.10 5.44 10.20 
cs6 6.78 5.14 1.18 1.66 7.24 4.27 1.38 8.90 
cs5 1.71 1.50 1.15 1.65 2.31 5.81 4.48 1.86 
cs4 2.04 2.51 0.27 1.58 4.24 3.04 2.90 2.02 
cs3 8.59 0.70 1.72 0.55 5.98 8.39 7.58 1.67 
cs2 1.70 0.37 0.44 0.32 3.47 0.82 2.70 2.33 
cs1 0.87 1.02 1.35 0.57 3.10 1.54 5.37 1.64 
Mean 3.14 2.09 1.02 1.44 4.39 4.57 4.26 4.09 
Error 1.92 4.33 
Relative error (%)Calibration
Validation
WSEMDHDMCVWSEMDHDMCV
cs7 0.31 3.37 1.01 3.75 4.43 8.10 5.44 10.20 
cs6 6.78 5.14 1.18 1.66 7.24 4.27 1.38 8.90 
cs5 1.71 1.50 1.15 1.65 2.31 5.81 4.48 1.86 
cs4 2.04 2.51 0.27 1.58 4.24 3.04 2.90 2.02 
cs3 8.59 0.70 1.72 0.55 5.98 8.39 7.58 1.67 
cs2 1.70 0.37 0.44 0.32 3.47 0.82 2.70 2.33 
cs1 0.87 1.02 1.35 0.57 3.10 1.54 5.37 1.64 
Mean 3.14 2.09 1.02 1.44 4.39 4.57 4.26 4.09 
Error 1.92 4.33 

WSE: water surface elevation; MD: maximum depth; HD: hydraulic depth; MCV: mean cross-sectional velocity.

Close Modal

or Create an Account

Close Modal
Close Modal