RESERVOIR SEDIMENTATION ASSESSMENT GUIDELINE - Aneel

Reservoir Sedimentation Assessment Guidelineis about 10% or more of bed material reporting the same diameter of the shield, orgreater. The shield computations suppose that a coarse layer will be built, as shown inFigure 13.3.y = height of original bed at the bottom of the shield layery a = degradation height or thickness of shield layerD c = diameter of the material building up the shieldy d = height of original bed at the top of the shield layer or degradation heightFigure 13.3 – Schedule for defining the shield (ICOLD, 1989)NA = Water levelEscoamento = runoffLeito original = original bedMaterial original do leito = original bed materialLeito degradado = sedimented bedFrom the figure, one may deduce that:y y ya= − d(13.2)By default:( )ya = Δ p y(13.3)where,Δp = percentage of material with diameter greater than the shield thicknessdiameter.Matching both equations, the degradation height is equivalent to:yd⎛ 1 ⎞= ya⎜−1⎟⎝ Δp⎠(13.4)The thickness of shield y a shall vary according to the particle diameter; however itis usually adopted as equivalent to 3 times the diameter D c of the shield particle, or15cm (0,5ft), or a little smaller.ANEEL – Brazilian Electricity Regulatory Agency / SIH – Hydrologic Studies and Information Department80