Washington modernized surface water mappingproject period: 08 01 2024 - 07 31 2026PROJECT abstract: the national hydrgraphy dataset (NHD) in washington has approximately 250,000 miles of mapped…

Washington modernized surface water mappingproject period: 08 01 2024 - 07 31 2026PROJECT abstract: the national hydrgraphy dataset (NHD) in washington has approximately 250,000 miles of mapped watercourses throughout the state and is a powerful, well-established framework used to analyze and associate critical information about our states hydrography. Since the adoption of the national hydrgraphy dataset NHD standard in 2011, washington state hydrography dataset program (washd) has focused its efforts on correcting the most prominent errors in the data and connecting the hydrography data to the highest priority water resources, water quality, human health, environmental monitoring, and fisheries datasets.ecology requested and received funding in the 2022 budget to conduct a two-year pilot project in the stillaguamish watershed to identify the technologies, methodologies, datasets, and resources needed to refine and maintain the accuracy of the washd. Work during year 1 of the pilot included an evaluation of the quality and accuracy of elevation-derived datasets and local hydrography data available in the watershed. As part of the continuing two-year pilot, project staff, and the washd steward, have been engaging with stakeholders across the state to understand the business needs, priorities, and challenges of these groups as part of developing the washd strategic plan. Survey data collected through this process has overwhelmingly showed that stakeholders identify accuracy as the most important factor for a useful hydrography dataset. The pilot project specifically tested the hydrography created using the elevation derived hydrography (EDH) specifications published by USGS. Results of the pilot project demonstrate that this dataset and EDH methodology significantly improves the accuracy of surface water mapped locations, creating a more accurate hydrography dataset that can be used at a local scale. Based on the data and methodology evaluations completed in fiscal year 2023, the USGS transition to its 3DHP, and the recommendation of the pilot project steering committee, ecology has requested and received state funding to complete updated mapping of surface water statewide. This project supports the purchase of EDH datasets that meet USGS specifications that can be incorporated into the 3DHP. The decision to start updating washd to 3DHP in the puget sound region was based on prioritization from stakeholders, available data, and technical considerations including available high resolution (QL1) lidar.while this project has broad support from washington hydrography stakeholders, there is also financial support from USFS which has jurisdiction on one third of the puget sound watershed. Washd has also been collaborating with the tulalip tribe to update a HUC8 in snohomish county.