• 濫用らんよう — abuse; using something excessively or improperly
• 氾濫はんらん — flooding; overflowing of water or information
• 濫発らんぱつ — issuing too many things (like licenses, money, or promises)
• 濫造らんぞう — churning out large amounts of poor-quality products
• 濫伐らんばつ — reckless logging; over-cutting forests

On the left, the radical 氵 brings in the image of flowing water. The right side comes from a character used for checking or overseeing things. When the “water” side overwhelms the container, the result is water that spills beyond its limits. That image was extended from literal floods to any kind of excessive or out-of-control behavior — the core idea of 濫.