Clarki, your'e right - pinks keep coming back which does indeed show their resiliency and ability to adapt, especially to shi**y environmental conditions. Also, pinks seem to be expanding their historical boundaries (ie. now fairly common in the Quesnel and Chilcotin systems) so they as a species do have something going for them.
But talking about the Vedder River, due to the low water levels ,the vast majority of incubating pink eggs that were deposited in the mainstem river below Vedder Crossing are toast. Thousands of fish were spawning in good quality but extemely unstable gravel; areas that today, in flood, were under 6 or more feet of turbulant, muddy, tree and rock scouring water. Many pinks spawned even lower, areas like the lower canal area, in silt. Gone.
It seems like Chilliwack pinks continue to thrive/survive by their ability to spawn in enough places that are not effected by these so often occuring natural events, areas like the (so important!!!) up river, non mainstem, off channel areas and Sweltzer Creek, as mentioned earlier.
Chris, I believe you are correct on lower river gravel extraction and it's negative effects.