If the equations have the same slope for example y=4x+2 AND y=4x+3 have the smae slope of 4/1, making them parallel but if the don't have the same slope for example y=2x+3 and y=4x+4 then they are not parallel
Well the chance of a hurricanes or tsunami damaging your city or house is greater. Another is that the soil closer to the coast can be a lot more moist, but that's not true for all places.
Infiltration depends greatly on the features of the soil. If the soil has excessive clay or mud, water will not find a way into the groundwater system and will remain as surface water.
An alluvial fan is a perfect location for this since there will be little or no resistance to the flowing water. The streams are already a connection with the groundwater system, and falling water will flow directly to it.