The primary consideration will be to paddle a kayak you can control, for most people preparing for coast to coast, this will be your race boat, the only one you own. There is limited value in paddling the river at a level beyond race parameters, and no value running it if you break yourself and /or your boat.
If I wrote down everything I consider when running the waimak this would be a novel rather than something people may read, so as a minimum.
1. Who is going on the trip, can people roll, what rescue gear does the group have and who can use it. As a minimum you need a first aid kit, kayak repair kit, split paddle, throw line (means you also carry a knife), extra food and clothes plus a shelter. If it all goes wrong could you loose one kayak and still have enough gear to spend the night?
The lower the experience, the lower the river level and the better weather you will need. Always remember it is a wilderness trip, look at the maps of the area, and know where you are and where the nearest hut or exit point is. Too many times I have had to patch up, evacuate or leave my gear with those unprepared.
2. Look at weather and rainfall data, what is the outlook and is it raining in the hills or has it been. It is far safer to paddle a dropping river than one that is rising. If you are not sure how much rain it takes to bring the river up then donít go until it has stopped raining and the river is dropping. Also for me anything over 45km of wind in the met service mountain forecast generally means a bad day out
3. Consider the flow:
ï When considering the flows remember Ecanís flows at the Motorway Bridge are tidal and the heights at Esk and the Gorge Bridge may change after floods as the river bed profile changes. http://www.ecan.govt.nz/Our+Environment/Water/Rivers/RiverFlows/river-fl...
ï All things being equal anything over 1m at Esk and/or 1.5m at Gorge Bridge will be outrageous for a lot of people and equate to 200 plus cumecs at the motorway bridge. Fine if you have the skills, just plain scary if you do not.
ï The most likely paddlable range for the race will be between .2 and .7 m at Esk, this is to allow for the lowest common denominator. If paddling skills improved this range would change.
ï If there has been coastal rain then it is possible for everything to look great down to the Esk confluence then go crazy, check Broken River on the way to the river, if it is discloured this is a good indication the river will change in the Gorge, another good indication of this could be the Gorge bridge levels changing out of step with the Esk levels, or Esk rising when there is clear low water levels at Mt White.
As always have a good day out there, it is a beautiful place to be.
(Kayaker and former Coast to Coast river official)
Assess the Risk, Own the Outcome