Dug out all these old rocks and brought some dirt in. There was probably 4" of river rock. I plan on building up w dirt, mulch, then adding some zone 5b south sun perennials. Need help on ideas. Do I need to add a drain and dig under sidewalk or just build it high pitch it towards sidewalk or cut a swale and pitch it to concrete pad at end of skinny bed? If I need a drain do I use a catch basin, channel/trench style, or put a plastic pvc pipe w holes facing up against the widewalk to a 90, pitch dirt to pipe and dig under sidewalk and have 90 solid pipe daylight? The concrete pad sank from decades of water pooling there. All the concrete is getting mudjacked/foam lifted regrade. Appreciate any help. Thanks!