The volcanic area is blessed with a lot of resources and cursed with eruptive disaster at the same time. Fertile land, deep forest, mining deposit, and water reserve are examples of the potential within a volcanic environment. The more productive activity is taking place, the more it risks damaged by a disaster. In 2010, Merapi, an energetic volcano in Java – Indonesia, erupted on a massive scale equal to one event in one hundred and seventy years. It was estimated up to 140 million m3 lahars produced, overwhelming installed sabo dams with only 20 million m3 in capacity. It damaged these sabo dams severely. Meanwhile, damaged sabo dams urgently needs to be either rehabilitated or reconstructed to set preparation against the next incoming eruption. This paper would focus on the estimation of functional performance given by the sabo dam at present actual condition. The aim is to create modelling framework base on structural equation modelling (SEM) and Generalized Reduced Gradient (GRG) Method. It adopts water resources principles, recent developed model, regulations and factors that influencing this purpose. All governing factors are grouped into three major classifications, i.e. physical aspect, regulative aspect and social aspect. These three aspect are consisted of eight dimension: sabo dam components performance, riparian vegetation condition, river course condition, sand mining performance, regulation conformity, socio-culture-economic, societal-private cooperation, and disaster loss then followed by thity nine indicators. The SEM result using SmartPLS from 89 sabo dam samples shows twenty six confirmed to be valid form thirty nine indicators, which the eight dimensions and three aspect remain intact. By the satisfactory statistical value of AVE (average variance extracted) > 0,5; CR (composite reliability) > 0,8; Cronbach Alpha > 0,8 and p ≤ α 0,1these twenty six indicators are: spillway, main dam, wing, drip hole, sub dam, apron, side wall, filling, parapet, parapet frame, and dyke under sabo dam components performance; vegetation species under riparian vegetation condition; roughness, depth, and slope under river course condition; legal mining, illegal mining and actual mining under sand mining performance; technical recommendation and sand mining license, under regulation conformity; local occupation, education and inhabitant economic, under socio-culture-economic; private corporate social responsibility (CSR) under societal-private cooperation; and public facilities damage, and husbandry loss under disaster loss.