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Published byPearl Henderson Modified about 1 year ago

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DESIGNING STONE TOE PROTECTION

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IS STP THE RIGHT SOLUTION? IS THE CHANNEL BED STABLE? IS THE BANKFULL WIDTH IN BEND LESS THAT 130% OF BANKFULL WIDTH AT RIFFLE IS UNVEGETATED POINT BAR LESS THAN 30% OF BANKFULL WIDTH AT RIFFLE

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Lanes Balance

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IS STP THE RIGHT SOLUTION? IS THE CEM STAGE IV OR V? IS THE RADIUS OF CURVATURE/BANKFULL WIDTH RATIO GREATER THAN 1.8?

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CONSIDER GRADE CONTROL!! A REALLY GOOD INSURANCE IS TO ADD A SMALL ROCK RIFFLE GRADE CONTROL TO YOUR STP PROJECT!!

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IF RADIUS IS TOO SMALL FOR RADIUS/Wbkf IS LESS THAN 1.8--CONSIDER USING “TRADITIONAL BANK PROTECTION”!!

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Scour Depth Assume Scour Depth will equal Max. Bankfull Flow Depth Assumes bed material allows full Sine Wave Flow to develop over time

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STP DESIGN START AND STOP AT STABLE POINT DESIGN HEIGHT SHOULD BE A MINIMUM OF 1.5 FT. ABOVE DOWNSTREAM RIFFLE ELEVATION DESIGN HEIGHT SHOULD INCREASE AS “BANKFULL DEPTHS” INCREASE AND/OR Rc/Wbkf DECREASES

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STP DESIGN GOAL IS TO PROTECT TOE IN AREA BELOW POINT WHERE VEGETATION CAN BE ESTABLISHED--- THEREFORE USE VEGETATION IN A “STABLE” AREA AS A GUIDE FOR REQUIRED HEIGHT OF STP

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STP DESIGN CREST ELEVATION SHOULD BE UNIFORM THROUGH OUT ENTIRE BEND ALIGNMENT SHOULD BE AS SMOOTH AS POSSIBLE “KEYS” SHOULD ALWAYS BE LOCATED AT U.S AND D.S ENDS

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STP DESIGN ADDITIONAL “KEYS” SHOULD BE PLACED AT REGULAR INTERVALS THROUGH THE ENTIRE REACH AT A MAXIMUM OF 100 FT. SPACING MAY BE SPACED CLOSER IN SMALL RADIUS BENDS (50-75 FT)

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STP DESIGN PLACE STP IN “WINDROW” WITH SMALL DEPRESSIONAL AREA BEHIND PEAK TO CAPTURE SILT AND CREATE A “BENCH” FOR VEGETATIVE GROWTH.

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QUANTITIES WILL VARY ALONG REACH DEPENDING ON WATER DEPTH USUALLY BEST TO FIGURE AVERAGE DEPTH THROUGH REACH TO CALCULATE QUANTITIES 1 TON/FT DESIGN WILL NOT BE 1 TON/FT FOR ENTIRE LENGTH TREATED

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QUANTITIES RIFFLE ELEVATION - MAX. BANKFULL DEPTH = MAXIMUM SCOUR DEPTH ELEVATION EXAMPLE RIFFLE = MAX. Dbkf= 4.0 FT. MAX. SCOUR DEPTH = 96.0

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QUANTITIES POOL DEPTH IS 3 FT. BELOW RIFFLE ELEVATION ANTICIPATE ADDITIONAL 1 FT. OF SCOUR--ADD ROCK TO LAUNCH INTO DEEPENED POOL WITHOUT LOSING CREST BY WIDENING CREST WIDTH.

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QUANTITIES CALCULATE AVE. HT. OF STP AS HT. ABOVE WATER + AVERAGE WATER DEPTH + ANTICIPATED SCOUR DEPTH END AREA IS APPROX. = 3H X H /2 = SQ. FT (1.5:1 SIDESLOPES) MULTILPLY BY 105 LBS/ CU. FT. AND CONVERT TO TONS/FT OF STP

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QUANTITIES EXAMPLE 1.5 FT. ABOVE WATER FT AVE. WATER DEPTH + 1 FT. ANTICIPATED SCOUR = 3.5 FT. OF STP 3(3.5) X 3.5)/ 2 = 18.4 CU. FT CU. FT. X 105 LBS/CU. FT. = 1932 LBS. = TONS/ FT

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SIZING MATERIAL 1. CHECK VELOCITY FROM I&E FORM 2. MULTIPLY MEAN VELOCITY BY 2 3. CHECK TABLE OF VELOCITIES TO MOVE DIFFERENT DIAMETER STONES 4. SELECT STONE SIZE WHERE MAXIMUM STONE WILL NOT BE MOVED

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STONE CLASSES

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SUMMARY CHECK BED STABILITY & Rc CHECK WIDTH OF CHANNEL AND POINT BAR CHECK ELEV. OF VEGETATION IN STABLE AREA ABOVE RIFFLE ELEV. CHECK POOL DEPTH

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SUMMARY (cont.) ADD---HT. OF VEG. ABOVE WATER AVE. WATER DEPTH IN REACH ANTICIPATED SCOUR DEPTH TOTAL = HEIGHT OF STP END AREA = 3H X H/2 VOLUME = END AREA X 105 LBS/CU. FT. (DIVIDE BY 2000 TO GET TON/FT)

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SUMMARY (cont.) MAKE CREST UNIFORM KEEP IT PEAKED KEEP IT SMOOTH BE SURE TO “KEY” IT IN SIZE STONE TO RESIST 2 X MEAN VELOCITY

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