How does turbine blade erosion in the low-pressure stages of a steam turbine impact the turbine's isentropic efficiency, and what is the main cause?

Turbine blade erosion in the low-pressure stages of a steam turbine significantly reduces the turbine's isentropic efficiency. Isentropic efficiency is a measure of how closely the actual turbine expansion process approaches an ideal, reversible adiabatic (isentropic) process, where entropy remains constant. Blade erosion roughens the blade surfaces and alters their aerodynamic profile, increasing friction and turbulence as steam flows over them.....