Plonimetered Shore Reireot 

 8.5(m)in50yr ; O.I7m/yr ;0.6fl/yr 



Withdrowal of Shoreline Due to Lower Woter- 



Stoi ion 1 77 1 2 to 1 76.66(ni) elevotwn 

 45 Il5m 



5 8,0m 



6 4.3 m 

 65 3 2 m 



67rD 



Wilhdrowal 



15 2m : 85 . 6.7m 

 '5-2'"/50yr = 0.304m/yr = lft/yr 



Between 1919 ond 1959 



00 100 200 300 



Figure 17. Historic .s'.ioreline change.<: in the vicinity of Per;trtater harbor. A 50- 

 year recession rate of 0.3 meter p ;r year was calculated using 1919 and 

 1969 shoreline po.sitions and correcting for withdrawal of the lake away 

 from the shoreline due to lower lake levels in 1969. 



Table 3. Comparison of historic with recent recession rates. 



1 Historic 



1 Recent 



Area extending COO !iiotcrs to 



either side of the i-entwator jetties 



Planimctcrcd aerial pliotos 

 adjusted for encroachment 

 (1910 - 1969) 

 Progradation on the north side 

 the jetties; recession on tiie 

 south side. 



3f 



Surveyed recession at four 

 stations 



(1967 - 19761 

 Progradation on the north; recession 

 on the south. 



Avg. recession rate: 0.30 



n/yr 



0.25 m/yr | 



50-kilometer study area, exclud 



ing sites of extensive modification by man | 



Surveyed bluff recession 

 (1838 - 1957) 



Power's (1958) Net recession 

 stations (m) 



85 35 



86 65 



87 66 



88 39 



Surveyed shore recession at 14 

 stations monitored from 

 1969 - 1975 



Avg. recession rate: 0.43 



n/yr j 2.54 m/yr | 



36 



