Surface erosion, reservoir sedimentation, channel sediment transport (including erosion and deposition) are integral components of watershed management, natural resources conservation planning, evaluation of water quality best management practices (BMPs), and total maximum daily loads (TMDLs) studies. These processes, encompassing surface soil erosion and sediment transport, have far-reaching implications for various critical aspects, including agricultural land productivity, the functioning of aquatic ecosystems, the recreational quality of rivers and reservoirs, the navigability of channels, and the operational flexibility of reservoirs in relation to water supply, environmental flows, and flood risk management objectives.
In this section, the utilization of HEC-HMS emerges as a valuable and indispensable tool for enhancing modelers' understanding of the potential impacts stemming from surface erosion and sediment transport within channel and reservoir systems on watershed dynamics. By leveraging the capabilities of HEC-HMS, modelers can achieve more reasonable predictions of peak flows and sediment transport, facilitating the simulation of diverse scenarios while incorporating essential hydrological and sediment data. This software provides users with a powerful tool to conduct thorough evaluations of heightened risks related to sediment transport. These risks encompass erosion and deposition within the system. By doing so, it facilitates the creation of robust strategies for erosion control, the maintenance of water quality, safeguarding critical infrastructure, and the establishment of sustainable water supplies.
This section delineates the techniques for addressing surface erosion, reservoir sedimentation, and channel sediment transport incorporated within the program. Especially, each of these methods of reach and reservoir elements calculates a sediment transport/routing downstream, utilizing an upstream sediment distribution as an initial boundary condition. The mechanism for achieving this involves solving both the continuity and momentum equations. Within this chapter, we provide a concise overview of the foundational equations, simplifications, and alternative model solutions.