I s'pose where you grow things that attract subterranean insects, that's where you will have mole tunnels as well. No insects in the chicken pen, right? But where Lyn is growing roses, enriching the soil, tilling and watering is a more attractive area for insects, so also for moles. My flower borders are mostly perennials and shrubs so not all that attractive to insects. Lawn grasses are a banquet to insects here, though. I've heard people say that what it takes to grow a beautiful lawn here is "chemical warfare" and that plus all the water, fertilizer and mowing is why County Extension encourages people to get rid of lawn.
Here in FL you often can't dig down more than 2 or 3 feet before you hit a dense clay layer. Probably our moles don't have their dens quite as deep, so that's why I was able to flood them out consistently.
Circling back to the original question as to why they come to the surface, no clear answer but I did find this line in the Wikipedia description:
"Moles have been found to tolerate higher levels of carbon dioxide than other mammals, because their blood cells have a special and unique hemoglobin protein. Moles are able to reuse the oxygen inhaled when above ground, and as a result, are able to survive in low-oxygen environments such as underground burrows."
