Generally you do not want to slow or stop the water from a downspout or the gutters will backup and overflow. The best option is to add a diverter at the bottom of the downspount and direct away from areas of concern.
You can install a splashblock at the bottom of the downsput to divert the water or you can install a French Drain to disperse the water into the ground.
If a downspout is gushing water then either it is too small or too much watershed is being fed to it. Consider enlarging the downspout or adding more drainage outlets.
Most down spouts are made to gush water but should be directed away from your house or walk way. You can correct this by installing a 90 degree bend or a splash block.
