On the point of divorcing your bivi bag? Teaming up with a tarp could save your relationship...
Bivi bags are ace when it's dry and fine, but not quite so clever when it's raining a bit and simple stuff like cooking, reading and keeping your hair, sleeping bag, clothing and other stuff dry becomes a Houdini-like juggling act. Or simply impossible.
One alternative is a lightweight bivi or backpacking tent with a hoop or poles to hold the fabric off your face and some shelter for cooking, but if you simply want to extend the range of your existing lightweight bivi bag, think about investing in a lightweight tarp.
A what? Essentially a tarp is a - usually - eyeletted sheet of lightweight, waterproof fabric which you can use to improvise some shelter from rain and wind and works well in combination with a bivi bag, particularly when it's not too windy.
Depending on the tarp and the situation you can rig anything from a basic overhead rain stopper through to a mini ridge tent affair with basic side protection. Use walking poles, sticks, handy trees, boulders or anything else which comes to hand to provide support.
In the UK, we'd be looking at something which gives as much protection from wind and rain as possible. As with tents, you need to position and orientate tarps with an eye on prevailing wind direction for maximum effectiveness - but get it right and you'll make bivvying altogether a more pleasant experience and, as a bonus, keeping your bivi bag drier means better breathability and less multi-day misery.
And of course, it's generally lighter than a tent too. Where do you find one? They may not quite be mainstream yet, but the guys over at Backpacking Light UK - www.backpackinglight.co.uk/page112.asp - have a wide selection from basic ultra-lightweight versions through to biugger communal tarps. They also sell a tarp DVD.
And then there's the Alpkit Tarp - a medium-sized fella with neat carabniner-style hanging clips and generously reinforced eyelet points.
Alternatively, tarps are simple enough that with some basic work, you can put together your own lightweight version as several OMers have already done - see links below this article and the image of Moprh's two-person lightweight above left.