This subtitle may not be construed as repealing any State law relating to water pollution or conservation. This subtitle is supplementary to those laws, except to the extent that the provisions are in direct conflict with one another. It is the purpose of this subtitle to provide additional and cumulative remedies to prevent, abate, and control the pollution of the waters of the State. This subtitle may not be construed to abridge or alter rights of action or remedies in equity under existing common law, statutory law, criminal or civil, nor may any provision of this subtitle, or any act done pursuant to it, be construed as estopping any person, as riparian owner or otherwise, in the exercise of his rights in equity, under the common law, or statutory law to suppress nuisances or abate pollution.