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EROSION TECHNOLOGY for SITES Earth Spillway Integrity Analysis Phase 2: Inputs and Equations. EROSION MEASUREMENT TRAINING: Maricopa County, AZ October 2011. SURFACE EROSION (Cover Destruction). 2. CONCENTRATED FLOW EROSION. 3 PHASE Spillway Erosion Model. 3. HEADCUT
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EROSION TECHNOLOGY for SITES Earth Spillway Integrity Analysis Phase 2: Inputs and Equations EROSION MEASUREMENT TRAINING: Maricopa County, AZ October 2011
SURFACE EROSION • (Cover Destruction) 2. CONCENTRATED FLOW EROSION 3 PHASE Spillway Erosion Model 3. HEADCUT ADVANCE
SPILLWAY EROSION PHASES 1. SURFACE EROSION (Cover Destruction) 2. CONCENTRATED FLOW EROSION (Headcut Formation) 3. HEADCUT ADVANCE
PHASE 2 CONCENTRATED FLOW EROSION
PHASE 2 Concentrated Flow Surface Detachment . r = kd (e - c) kd = coefficient of detachment (material property) c = critical tractive stress (material property) te = g(d+Dd)S Stress equation applies when eroded depth (Dd) is less than approach critical flow depth (phase 2).
er tc te
DETACHMENT RATE COEFFICIENT The detachment rate coefficient may be externally determined and entered directly in SITES or estimated by SITES from soil properties.
Summary of Factors to compute Kd • Dry Density, gd • Percent finer than 2m (% clay) • Practical range is from 0.01 to 10 • Number is inversely related to resistance to erosion – low value is high resistance, high value is low resistance • Note units are in ft/hr of downward erosion per unit applied stress of lb/ft2
CRITICAL STRESS for Detachment Critical stress based on loose particle condition for all materials.
SPILLWAY EROSION PHASES 1. SURFACE EROSION (Cover Destruction) 2. CONCENTRATED FLOW EROSION 3. HEADCUT ADVANCE