The comments on the pond shape are spot on. You will need many more bottom drains than 4 and many, many TPRs (Tangential Pond returns) to get some kind of flow in that design.
When we do a design we have to set criteria. If it is a water garden with the most important aspect the "look" then we plan for the look and the fish are secondary. If our goal is to build a pond for fish, the most important part of the design is the environment in which the fish live. Yes, we can make these look fantastic, but water movement is a primary consideration.
While not having the space to discuss every point of pond design here in a couple of paragraphs, I can recommend two resources for you. One is the book by Peter Waddington titled Koi2Kichi. While not an inexpensive book the amount of time and frustration that you will save will make it a fabulous bargain. For an on line resource try this link, it is the best that I have found for an on line, step by step, true koi pond guide:
http://www.koicymru.co.uk/construct.htm
Please do more research before you put the shove in the dirt so to say. If you don't you will not be much different than the average ponder like myself. I am currently on my fourth pond build. As Peter Waddington has said and I totally agree the least expensive way to build a proper koi pond is to build it once, the right way. Please learn from people like me who have spent way more than any one man should have to spend to get a proper pond. Leave the emotional rush of having to have it now behind for some more research. The choice is yours of course. One thing nice about this hobby is that it is not a race to the end, but a wonderful journey that involves an exciting learning curve. Have fun and enjoy it.
Rick