This first picture is of a river that runs straight through parts of Hiraka City and appears in my neighborhood. I am not sure on the purpose, but I assume that it protects people during rainy season or typhoon season when water levels may pose a threat to the neighbor hoods and city areas. I also think it serves as some kind of drainage for house water, but not polluted water.
I really like this river though because it is peaceful with lots of wild life. People can easily access it at some sections with stairs to walk their dog, throw their kid into the water, or to sit on the edge and relax. It is clean and enjoyable for everyone. Some parts are not pretty, but river represents city life: flowing peacefully yet always busy with work, school, or izakaya.