Designing the alternatives NRMLec16 Andrea Castelletti Politecnico di Milano Gange Delta

2 ICT Tools yes Final (political) decision reasonable alternatives 2. Conceptualisation 3. Designing Alternatives 4. Estimating effects Stakeholders 1. Reconnaissance 5. Evaluation no Mitigation, and compensation, Agreement? PIP procedure PIP Participatory and Integrated Planning procedure 6. Comparison or negotiation

3 Which alternatives to consider Very often the alternatives considered in real world projects are only those proposed by the DM and/or the stakeholders or suggested by the Analyst’s experience. It is suitable to consider for evaluation all the alternatives that can be obtained by combining in all the possible ways the actions identified in Phase 1. Eg. Verbano project s storage disch. curve f regulation range d MEF value p regulation policy ACTIONS It is a 2-element finite set Infinite sets politicies range MEF SDC curr politicies range MEF SDC +600 Infinite alternatives

4 Design problem The design problem Usually, even if not always infinite, the number of alternatives can be very high, therefore one should identify the “most interesting” ones “most interesting” according to the criteria expressed by the Stakeholders. The indicators associated to such criteria are transformed into objectives and the alternatives which are efficient with respect to those objectives are identified.

5 Full rationality conditions The solution of a design problem is usually complex because: dealing with multiple, often conflicting, objectives a single criterion to select the aternatives is not available. SIMPLIFICATION: full rationality There exist only one project indicator This situation is not relevant if the aim is to apply a participatory paradigm to decision making, indeed: either only one Stakeholder exists, a very unlikely situation; or the Analyst is considering only one objectives, thus ignoring the Stakeholders (e.g. Cost Benefit Analysis): no participation. !

6 Project indicator The project indicator should be such that, given two alternatives A1 and A2, if i(A1) < i(A2) then A1 is preferred over A2. The optimal alternative is the one for which i takes its minimum value. For example: i cannot be an indicator like the wet surface area S of a wetland In altre parole: i should reflect the satisfaction produced by the alternative, i.e. its Value. V S

7 ICT Tools yes Final (political) decision reasonable alternatives 2. Conceptualisation 3. Designing Alternatives 4. Estimating effects Stakeholders 1. Reconnaissance 5. Evaluation no Mitigation, and compensation, Agreement? PIP procedure PIP Participatory and Integrated Planning procedure 6. Comparison or negotiation OPTIMAL ALTERNATIVE It is required: When two models are used; To validate the results.

8 Complexity of the full rationality problem Even with only one project indicator (full rationality) the problem can be particularly complex, because of 1. The existence of infinite alternatives; 2. The uncertainty of the effects induced by the presence of random disturbances; 3. The existence of recursive decisions.

9 Infinite alternatives With a finite (and small enough) number of alternatives: exhaustive procedure  for each alternative A compute when i is a cost, the optimal alternative is the one that min i With an infinite (or very big) number of alternatives a procedure should be used through which the optimal (or a nearby) alternative is singled out by analysing only a small number of alternatives.

10 Uncertainty of the effects The alternatives can not be ranked with respect to i... random indicator (stochastic or uncertain) random disturbances --- Example Project: construnction of bank on a river to protect from floods. Decision: high u P of the bank i = discounted future damage + construction costs i changes with the trajectories of the level This is not known (it is random!) when u p has to be selected. For a given u p many values of i can occur. What can we do?

11 Uncertainty of the effects The alternatives can not be ranked with respect to i... random indicator (stochastic or uncertain) random disturbances --- Example Project: construnction of bank on a river to protect from floods. Decision: high u P of the bank i = discounted future damage + construction costs i changes with the trajectories of the level This is not known (it is random!) when u p has to be selected. For a given u p many values of i can occur. What can we do? The uncertainty must be filtered: a deterministic value of i is associated to each u P. 1) If i is stochastic the probability distribution is identified, if i is uncertian the corresponding set-membership. 2) Based on appropriate statistics the optimal alternative is selected In our example: u P is selected such that the expected value of i is minimum (min E [i]) u P is selected s.t. the value is minimum in the worst case (min max i) The uncertainty must be filtered: a deterministic value of i is associated to each u P. 1) If i is stochastic the probability distribution is identified, if i is uncertian the corresponding set-membership. 2) Based on appropriate statistics the optimal alternative is selected In our example: u P is selected such that the expected value of i is minimum (min E [i]) u P is selected s.t. the value is minimum in the worst case (min max i) disturbance filtering criteria

12 Recursive decisions recursive decisions They can be transformed into a planning decision by defining a management policy, which, in the simplest case, is a perodic sequence of control laws m t () How to define them?

13 Reading IPWRM.Theory Ch. 7