# We’ve changed the way it rains

Learners involved: 1 class high school

Age from 14 to 15

Rising temperatures make the planet hotter and also knocked longstanding precipitation patterns off balance by altering how much water cycles between earth and the sky.

Learning Objectives:

Students will be able to:

• Know the difference between wheather and clime
• Analysis and comparing data visualizing
• Elaborate a solution Nature Based (NBS)

Activities

The students start to work together observing whether of our country, Pomigliano D’Arco, a small town located 37m above sea level with a  warm and temperate climate.  Rains were particularly abundant and frequent in November and December by analyzing data collected by our meteorological station.  They observed that in the last 15 days of December 101.1mm of rain fell which is the same amount measured in the last year determining  (flooding) due to the inadequacy of collection systems. The excess flow rates discharged to the surface by the pressurized sewer can fill any depressions present on the ground, or flow-through preferential routes, creating a flow network that in urban areas affects roads, sidewalks, natural depressions and small streams. When rainfall is particularly intense, conditions of increased hydraulic risk are generated which impact people and infrastructures. The students understood that the reduction of permeable areas – reduction of vegetated areas – reduction of surface reservoirs is the problem.

Main results and conclusions

Highlights how the transition from agricultural land (natural cover) to a completely waterproofed surface (square, asphalted and/or cemented road, etc.) leads to a progressive reduction of the infiltration coefficient c. the. (represented by the amount of water that infiltrates in conjunction with meteoric precipitation) and an increase in the surface runoff d.s. (part of precipitation flowing to the surface).

Example of calculation

Asphalted surface – schoolyard c.i. = 15% d.s. = 55% (with peaks of up to 80%).

Agricultural land – adjacent cycle path c.i. = 50% r.a. = 10%

The increase in the size of surface runoffs is evident where the soil replaced by impermeable areas. It should be borne in mind that during particularly intense hourly rainfall (in the order of 70-80 mm / h) the urban drainage system can go into crisis, causing localized flooding that seriously impacts anthropogenic structures. The forecast implies that the amount of water that will fall in the coming years will be less and less, despite the damage from flooding, floods … have been growing in recent times.We can give an explanation to all this, saying that on days when it rains, the rain is very intense, which cannot be disposed of by the current sewage works.

The students use the NBS  methodology  elaborate a project on infrastructures, correlating nature and the urban environment. The idea is to create urban drainage channels able to drain excess rainwater along the edges of the roads (Figure ).