HELM engineers have a long history in the development of large-scale drainage master studies and plans that define and quantify the extent and magnitude of flood hazards and risks. These studies are aimed at providing documentation of potential flooding impacts for existing conditions and future developments to local, county, state, and Federal agencies. Information provided by these studies is used to identify high-risk flood prone areas requiring flood mitigation as well as to guide future development. Identification of flood hazards and risks are undertaken using a suite of tools and datasets such as: 1- and 2-dimensional rainfall-runoff models, detailed topographic mapping and planimetric features, soils data, and land-use data. Study results are organized and presented in a way that offer planning alternatives and associated costs for stakeholder consideration.
A selected recommended planning alternative may consist of a combination of flood control infrastructures, such as: storm drains, channels, culverts, detention basins, drop structures, levees, impoundment structures, or certain land management treatments designed to collect and infiltrate rainfall where it falls. After identifying specific treatments to mitigate flood hazards, HELM’s design engineers are able to prepare drainage master plans that include, but are not limited to, the following: engineering design concepts, construction drawings and specifications, and an engineer’s estimate of probable cost for the proposed flood protection facilities. Also, a Conditional Letter of Map Revision (CLOMR) may be necessary to revise existing FEMA flood maps. The overall objective is to integrate these components to develop a solution that is cost effective, provides a high level of flood protection, and avoids adversely impacting natural and cultural resources to the maximum practical extent.