Can a sand dam be built anywhere? There are three technical prerequisites for locating appropriate sand dam sites. Firstly, it needs to be built on a highly seasonal river (flowing for weeks rather than many months of the year). Secondly the river needs to have sufficiently sandy river sediment. Thirdly, there must be accessible bedrock to dig down into. And Excellent Development has established two golden rules for sand dam design. The first is that dams must be built on bedrock (or, in rare cases, impermeable, compacted sub-soil). Secondly, the dam must allow the river to flow as it did before. For more in-depth guidance on how to design and build sand dams, read our sand dam manual.