Watershed Management Program

Topographic InformationWatershed Evaluation

Watershed Management PlanImplementation of Best Management Practices

Maintenance of Watershed Parameters and Models

Project Development

• Project issues and approach outline• Project timeline, and staff allocation and cost

spreadsheet• Project communication and quality assurance

plan

Digital Topographic Information

– Horizontal and vertical datum establishment;– Collection of existing topographic information and

generation of topographic feature classes necessary for building a DTM of the watershed;

– Datum conversion;– Identification of topographic voids;– Acquisition of topographic information using aerial

methods or other approved methods;– Triangulated Irregular Network (TIN) and Digital

Elevation Model (DEM) for Watershed Evaluation processing;

– Project management and quality control; and– Final approved deliverables for Digital Topographic

Information.

Watershed Evaluation– Generic watershed feature assembly, evaluation, and processing from

existing data sources;– Field data acquisition approach to refine DTM and hydraulic features

(locations, methods, and accuracy);– Public Notification – Field reconnaissance and acquisition of additional spatial (xyz)

information and attributes for DTM and hydraulic feature refinement;– TIN and DEM refinement based on added information from desktop

evaluation and field reconnaissance;– Generic hydrologic features;– Generic hydraulic features;– Surface water resource assessment analysis approach;– Project management and quality control; and– Final approved deliverables for the Watershed Evaluation.

Watershed Management Plan – Refined generic and semi-generic geodatabase, and parameterization for specific use

geodatabase or database;

– Watershed computer simulation model development and verification;

– Floodplain analysis and delineation;

– Public notification, public meeting and 90 day review and comment period;

– Revised floodplain analysis and delineation based on public comment and review;

– Level of service determination;

– Digital Flood Insurance Rate Maps (DFIRM) generation;

– Surface water resource assessment;

– Best Management Practices (BMP) alternative analysis;

– Project management and quality control;

– Final approved deliverables for Watershed Management Plan; and

– Conceptual Environmental Resource Permit application(s) for Selected BMP(s). (optional)

Issues

• Rainfall excess method for Floodplains– SCS/NRCS not reasonable for floodplains in watersheds

with deep type A soils– Dynamics of saturation excess and level of detail– S or total retention storage, including initial soil storage.– Storage threshold for Initial abstraction in the hydrology

and storage threshold for dynamic storage (explicit in the model)

• One day ERP, Five day for floodplains• Percolation as an outfall for storage areas • QA/QC, Public review and comment • Maintenance and FIRMs effective flood hazard zones • Event Based rainfall. Spatial and temporal

distribution of the design event

• Overland Weirs in 1-D unsteady state models – Connected reservoirs or channel to a

reserviors

• Storage threshold for Initial abstraction in the hydrology and storage threshold for dynamic storage (explicit in the model)

• The G&S is not an excuse, not to think.