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W.D.O.T. FACILITIES DEVELOPMENT MANUAL <br /> EROSION MAT DESIGN <br /> Description: <br /> Swale A(Average Slope 20.0%) <br /> Given: <br /> CHANNEL CROSS SECTION <br /> 11=11 <br /> =nii i,l-a=1 Width(W)=2 feet <br /> 1—h 3 A-4=11= <br /> =11 <br /> i _11 Depth(D) = 0.14 feet <br /> °11= �N11 Sloes 0.20 ft/ft <br /> 1:I=u=Il =u=n= <br /> 1=11=11=11=11= <br /> Calculate w <br /> Calculate maximum shear stress in the swale, Tm: <br /> �m = yds = (62.4 lb/ft2)(0.14 ft)(0.20 ft/ft)= 1.74 lb/ft2 <br /> WDOT Class II, Type B coconut erosion mat=2.0 lb/ft2 <br /> (Permissible Shear Stress per Facilities Development Manual 10-5-35 Figure 1) <br /> Description: <br /> Swale B (Average Slope 1.0%) <br /> Given: <br /> CHANNEL CROSS SECTION <br /> 11=1i h <br /> =11-_ 1=11-1 <br /> n ,1r= Width (W) = 2 feet <br /> —1ia1_ 3 i._z11- . <br /> .u� o __I�.n=1 Depth (D) =0.20 feet <br /> = ' "� Sloes 0.01 ft/ft <br /> n-al—n=n 11=11= <br /> L=u=11=u=n=: <br /> w <br /> Calculate maximum shear stress in the swale, 'Lm: <br /> �m =yds = (62.4 lb/ft2)(0.20 ft)(0.01 ft/ft) =0.12 lb/ft2 <br /> WDOT Class I, Type B erosion mat= 1.5 lb/ft2 <br /> (Permissible Shear Stress per Facilities Development Manual 10-5-35 Figure 1) <br /> Stormwater Submittal <br /> PC-03-15 <br /> 5/26/2015 Exhibit#4 <br />