private String produceRivers() {
		findRiverOrigins();
		findRiverEndings();
		
		int c = 0;
		for (Point r : rivers.values()) {
			if (details) System.out.println("Developing river: "+c);
			developRiver(r, false, c);
			c++;
		}
		
		if (ioflags.SAVE)
			produceImage();
		
		return "No errors.";
	}