The predictions of wave attenuation from vegetation are associated with considerable uncertainty in practical engineering, because practitioners often must select dissipation coefficients from empirical datasets and extrapolate from small-scale tests. The present work proposes an analytically based method to evaluate the dissipation coefficient for spectral energy conservation models based on fixed hydrodynamic force coefficients: invariant of sea state and vegetation characteristics. The approach is applied to data from two experimental campaigns with the results demonstrating considerable success and potential application for the proposed method. The method will enable practitioners to explore and apply an alternative and more robust approach compared to the conventional use of empirical datasets. Using fixed hydrodynamic force coefficients, whereby greater accuracy and reliability is achieved, will enable practitioners to more effectively and directly compare various layouts of natural and nature-based solutions using quantitative methods. Future work includes extension to an irregular wave formalism and application to field data.