what is its index?
One of the measurements is the geometric index of reduction.
Lithic reduction
One of the measurements is the geometric index of reduction. 
what is referred as bull run river? It is a tributary of the Sandy River. where is it situated? U.S. state of Oregon who were its first inhabitants? Paleo-Indians how is the climate here? mild climate is it related to any energy producing project? UNANSWERABLE how is the above mentioned group of people classified? They  are generally classified by lithic reduction or lithic core "styles" and by regional adaptations. when did they migrate to america? 17,000 years ago you mentioned a kind of reduction in you answer, what is that? It is the process of fashioning stones or rocks from their natural state into tools or weapons by removing some parts.
wiki:1155883
Lithic reduction [SEP] Reduction index
By understanding the complex processes of lithic reduction, archaeologists recognize that the pattern and amount of reduction contribute tremendous effect to lithic assemblage compositions. One of the measurements is the geometric index of reduction. There are two elements in this index: 't' and 'T'. The 'T' is the 'height' of maximum blank thickness and the 't' is the height of retouched scar from the ventral surface. The ratio between t and T is the geometric index of reduction. In theory this ratio shall range between 0 and 1. The bigger the number is the larger amount of lost weight from lithic flake.