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Cheapest solutions


I've been trying to understand RIOS a bit more by working on the Rimac watershed here in Lima and have encountered two problems:

1. Why is the focus so clearly on the cheapest option, and only after I spread the budget evenly will the program suggest other investments than fencing? (See RIOS1) 

1. If I do tell the program to spread the budget over all activities (in an attempt to remedy problem 1). Why are my results so scattered? Is there any way I can try to "clump" these a bit more? (See RIOS2)   

Thanks very much in advance!

1903 x 1753 - 366K
1903 x 1753 - 187K


  • adrianvogladrianvogl Member, NatCap Staff
    Hi Els,
    1. The issue of cheapest option being preferred has to do with the way that RIOS calculates the cost-effectiveness scores for each activity.  First, RIOS calculates the effectiveness score for each activity.  Then, it divides this score by the cost of the activity.  I see that you have activity costs ranging from 704 to 11,586. If the activities are associated with similar transitions, then it is likely that the effectiveness scores are the same.  So when the scores are divided by the costs, this order of magnitude difference in your costs means that the cost-effectiveness scores across the whole study area will be an order of magnitude lower for the cheapest activities, and so RIOS will not choose the more expensive activity.

    For now, RIOS works best if you consider activities that have more similar costs (within the same order of magnitude), or if you allocate the budget to different activities (as you noticed).  You can also think about adjusting the activity costs to reflect differences in their effectiveness, thereby forcing the cost-effectiveness scores to be more in line.  For example, consider that you have two activities: activity A that costs 100 and activity B that costs 250.  Activity B is twice as effective as activity A.  You could adjust the cost of Activity A (100 * 2 = 200) to reflect the fact that twice as much area must be implemented to achieve the same benefit as with Activity B. 

    This is a known limitation of RIOS and something that we are working on developing a way to fix, but unfortunately I don't have a good estimate of when this fix might be released.

    2. RIOS used to include an option of a "clumping factor" that would aggregate activities in space.  But, there were problems with how this worked in practice, so we removed it in the last versions.  RIOS will select pixel by pixel starting with the highest cost-effectiveness score and working down until the budget is spent.  That means that often the activities will be more scattered across the landscape.  In practice, you could use RIOS outputs to guide activity locations, and focus on the places where the most activities are seen in close proximity to one another.   
    One option is to use RIOS to identify “hotspots” for each activity, and manually create portfolios based on these.  For this approach you could run RIOS, and instead of looking at the activity_portfolio_total output, look instead at the activity scores directly.  These are saved in a folder called “/activity_scores” and there will be one score map per activity.  If you overlay some boundaries that are applicable to your project and where you might want to prioritize activities (like microwatersheds), then you can see which microwatersheds have the highest scores for each activity (by running zonal statistics, for example).  This would help if you want to prioritize microwatersheds (or other administrative unit) to target activities to. 

    3. Finally, please check that you are running the latest version of RIOS (we are now on 1.1.13).  I noticed a strange horizontal striping in your RIOS2 outputs that has most likely been fixed with a later version.

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