<p> A simple technique to estimate the hydraulic impacts associated with the deployment of hydrokinetic (HK) devices is introduced. This technique involves representing HK devices with an enhanced bottom roughness. The enhanced bottom roughness is found to be a function of Manning roughness, slope, and water depth of the natural channel as well as device efficiency, blockage ratio, and density of device deployment. This approach was developed using a theoretical relationship between power extracted to power dissipated, and assuming a simple rectangular channel cross-section and uniform distribution of devices. Once the effective bottom roughness is determined, it can be used to determine the hydraulic impact of arbitrary device configurations and flow situations. The enhanced bottom roughness approach was compared to an alternative method of determining the affects of hydrokinetic energy extraction (SNL-EFDC). Both methods were in good agreement. Capabilities and limitations of determining hydraulic impacts by enhanced bottom roughness approach are demonstrated by site-specific simulation for the Tanana site. </p>