Equivalent circuit to use when calculating the impedance of an electrical cable from its datasheet parameters
If your operating at DC maybe, if you ever plan on switching the signal, then no. Why? because transmission lines have wave effects.

Especially if your cable is a long enough to be a transmission line, here is how you'll know:


  A cable becomes a transmission line when it has a length greater than
  λ/8 at the operating frequency where:
  
  λ = 300/fMHz
  
  For example, the wavelength of a 433-MHz frequency is:
  
  λ = 300/fMHz = 300/433 = 0.7 meters or 27.5 inches


So find the highest frequency that will travel through the cable and "plug and chug"

Really what you need to do is use a transmission line model, the power source, cable and load all need to be matched, otherwise you will have:
1) Not optimal power transfer
2) Reflections and other problems. 

So, Find the characteristic impedance of your cable and match 



If your cable is short, then you could probably approximate the cable with this model (kind of like yours, but don't forget G)


Note: I think the problem is you need to also look at the load, its just easier that way. I simulated this with ltspice and the lumped element model but also the resistance and inductance of the return current. I am graphing the combined cable and load impedance. I see frequency effects above 10kHz with a load of 1Ω (green line), for 100Ω (red line) your good to ~1MHz, 10kΩ (purple line), you start to see frequency effects show up at 5MHz.