I am interested in calculating the economic value of the sediment loss, by calculating the total direct and indirect cost involved in conserving the area from soil erosion (bunding, terracing and mulching)? Is there any model which I can use?
I am not sure whether this is helful for by but there is a study (CSERGE Working Paper GEC 96-13) by Rebecca Clark that introduces into the valuation of the on-site effects of soil erosion by taking into account (i) the impacts on soil properties, considering the soil as a resource, and (ii) the impacts on crop production (i.e. agricultural productivity of soil). The study by Anasiru et al. (2013; Economic Valuation of Soil Erosion on Cultivated Drylands in Langge Sub-watershed, Gorontalo, Indonesia), particularly looks at the loss of soil fertility by erosive processes in order to aim at the economic valuation of soil erosion. Eaton (1996; The economics of soil erosion: a model of farm decision-making), for instance, gives a summary on the literature economic analysis of soil erosion and conservation.
If you have access to production (and preferably input and output price) data you can value environmental resources as inputs and derive their contributions to enterprise profit. Several authors around the 1990's used this approach to value such things as air quality, soil health and watershed attributes. Two references are Vincent ('The environment as a production input' 2008) and McConnell and Bockstael in volume 2 of the handbook of environmental economics. This approach eventually provides a 'revealed' value for the environmental asset and is as robust as the production models you employ. I am currently using it to value environmental health for the rangelands of Australia using a beef production model (simple Cobb-Douglas) and think it is an often overlooked approach which has strong merits from an economic perspective.