So sorry! Looks like the dry, brown branches mean this shrub has died. Are there any green branches left? If so cut off all the brown branches, water well and perhaps the shrub will come back in the spring. When I see sections of a shrub dead and brown and other branches on the same plant green and healthy I suspect root damage from a mole or vole or branches there were broken from a physical injury such as a basketball hitting the shrub. I really can't tell if the green branches are on the sickly shrub or if they are on the neighboring shrub. The good news is if you remove the sickly shrub the other spiraeas nearby should fill in the space. You do not need to dig up the roots just cut the shrub to the ground and see what happens. Keep growing, Marianne Binetti