Thanks for submitting your question. First, I applaud your desire to try to return the stream to its historic state. We usually receive questions regarding the opposite - how to build and maintain ponds.
It is pretty challenging to address your question without seeing the situation. I would be happy to take a look at your pictures. Feel free to email me at my address below, or call me directly - 503-510-7582.
There are a few things to consider about your situation. If it is pretty small, it may be as easy as removing the outfall (i.e. small dam) and letting the stream adjust. However, depending on the size and amount of sediment that has built up, this could cause a lot of fine sediment to wash downstream and your stream to erode as it tries re-establish its slope. What are the dimensions of the outfall (height, width) and the pond? What is the max depth of the pond?
The next factor is whether you have any non-native fish, wildlife or invasive aquatic weeds that might be sent downstream. Do you know if you have any of these?
The final factor is whether you will need any permits to be moving and filling the wetland area. I am guessing that this will not be necessary since it is "human-made" and it sounds pretty small. Even so, depending on size and location, you should have a natural resources professional take a look to provide guidance on how to fill and plant the area, and let you know if any permits are necessary.
I have had good luck with contacting my local county Soil and Water Conservation District for an initial visit and suggestions. This would be Hood River SWCD - http://hoodriverswcd.org/
. If they do not have the expertise, they are usually pretty good at knowing other local professionals that would be willing to help at no charge.
Feel free to send pictures and follow up by phone/email if you would like. I am sorry that I don't know a specific person in your area to contact for help.