To reduce economic costs and environmental effects when developing hydroelectric energy, what are some strategies that can be used? Select all that apply.

a. Select a river with low flow so that construction of a dam is a small, manageable project.
b. Develop on a site that requires deforestation so timber can be sold to offset construction costs.
c. Ensure that raw materials for construction are available close by.
d. Choose a site where the river narrows and there is a natural reservoir further upstream.
e .Make sure to not divert hydrological flow.