Heavy rains are a problem. They run off pavements, get poisoned, are funneled into storm sewers, and have to be managed. In the country they run off depleted soils, damage bridges and roads, and create floods. Some solutions have already been proposed. This overview emphasizes education, changing building codes and regulations, and removing financial barriers.
Encourage homeowners to use rain water – watering lawns, gardens, and farm fields, and with metal roofs for household use. This will require education (about safe use and purification),
infrastructure such as cisterns, purification devices, and gutters can be encouraged through
financial support such as tax breaks, loan and grant programs, and technical support.
Note building codes comments below.
Other buildings can be treated similarly – apartments, offices, schools, industry.
Farms and rural spaces:
Support better water management, including use of swales, ponds, and underground storage to save rain on site for dry periods,
Support cover cropping and crop rotation, so a heavy rain is kept to water crops instead of carrying off degraded topsoil and creating floods.
Support includes regulations, building codes, technical support, tax structures, loans and grant programs.
Pay for it with cost savings on infrastructure and flood prevention.
Current building codes prevent builders and homeowners from making houses in ways that conserve water. These codes could be changed to encourage conservation.
Begin where it's easy: Homeowners who want to build differently (rainwater collection, composting toilets, greywater systems) are currently prevented by state law or discouraged by difficult requirements. Change this. Financial and technical support would help.
New construction will be built to conserve rather than waste – dual plumbing so greywater is used to flush toilets, for example.
Encourage voluntary retrofits.
Examples of alternatives: composting toilets as a norm in the country, potable water requirements (for instance, rain water from a metal roof properly filtered), greenwater and graywater for garden and yard usage, dual plumbing systems to safely optimize use of both rainwater and graywater. Proper use of on-site water decreases runoff problems.
Three aspects: changing codes, offering technical support and assistance (education to builders and homeowners), and cultural change normalizing non-wasting and safe handling (for example, educational programs normalizing traditional non-wasteful, safe practices such as those used by our ancestors, and distinguishing between safe and risky use).
In short, change codes to reflect the needs of the whole society, educate people in safe use, and change cultural norms through education.