A lot goes into designing rain gutters. Depending on the area, the wind, the weight of a gutter with water, water flow rate, rain effects, strength of the gutter, etc.
You also get a wide variety of materials for the gutters such as:
Rain water collection systems are used in western countries to collect water from rooftops and release it where the effects will be least harmful. Gutters also help prevent water from seeping into a structure by ensuring the water does not run down the side of the building.
In many developing and some developed countries rain water capture systems are used to collect rain water for potable use. This use of rain water collection inherently requires more reliability as service interruption can immediately effect users. Many parts of the world also lack necessary skills and tools to repair broken or damaged systems causing many to fall into disrepair.
In many parts of the world heavy storms can cause damage to gutter systems and this must be planned for in the initial design. In some areas these heavy storms can also be the only rainfall over long periods of time so the systems need to be able to operate during these periods. The effect of water on the degradation of structural material must also be considered.
Rain gutter systems collect and transport water to desired locations. Their function becomes increasingly more important once they begin to be used for collecting water to be used for drinking. Most of the current systems that exist are designed to withstand western style storms. They are also designed to fit to standard western buildings. Improvisation with an understanding of the fundamental design challenges should lead to better gutter design for critical applications in the developing world.