DESIGNING STONE TOE PROTECTION

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

Lanes Balance

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

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

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

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

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

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

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

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)

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

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

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

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.

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

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

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

STONE CLASSES

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

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)

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