# HAND – Height Above Nearest Drainage (`HAND_Height_Above_Nearest_Drainage_m`) — EDIS AI Agent Dataset View

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## 1. Dataset Metadata
- **Raster Name**: HAND – Height Above Nearest Drainage
- **Slug**: `HAND_Height_Above_Nearest_Drainage_m`
- **Units**: `Meters (m)`
- **Spatial Extent**: UL(90.125, -180.0) to LR(-90.1219617, 180.1247159)
- **Summary**: The Height Above Nearest Drainage (HAND) raster represents the vertical distance (in meters) between each land surface location and the nearest hydrologically connected drainage channel. Lower values indicate areas closer to river systems and floodplains, while higher values represent elevated terrain.

HAND is a key indicator of flood susceptibility and soil saturation potential, with low-lying areas more likely to experience prolonged wet conditions and reduced oxygen availability.
- **Included in Flagship Map Package**: `Global_ISO9223_2020_2024_LE_V4` (`GET https://secure.engineeringdirector.com/api/bundles/Global_ISO9223_2020_2024_LE_V4/point_query`)

### Color Table & Value Breaks
- `(0.0, (0.0, 100.0, 0.0))`
- `(2.2, (5.0, 105.0, 0.0))`
- `(4.4, (10.0, 110.0, 0.0))`
- `(6.6000000000000005, (15.0, 115.0, 0.0))`
- `(8.8, (20.0, 120.0, 0.0))`
- `(11.0, (25.0, 125.0, 0.0))`
- `(13.200000000000001, (30.0, 130.0, 0.0))`
- `(15.400000000000002, (35.0, 135.0, 0.0))`
- `(17.6, (40.0, 140.0, 0.0))`
- `(19.8, (45.0, 145.0, 0.0))`
- `(22.0, (50.0, 150.0, 0.0))`
- `(22.0, (50.0, 150.0, 0.0))`

<h2>Technical Specifications</h2>

<h3>HAND – Height Above Nearest Drainage</h3>
<p><strong>Global | ~1 km Resolution</strong></p>

<h4>Raster Name</h4>
<p>HAND – Height Above Nearest Drainage</p>

<h4>File Name</h4>
<p>HAND_Height_Above_Nearest_Drainage_m.tif</p>

<h4>Short Description</h4>
<p>
A global terrain-derived raster representing the vertical elevation difference between each land surface location and the nearest hydrologically connected drainage channel.
</p>
<h4>How to Read This Map</h4>
<ul>
  <li><strong>Lower values</strong> indicate areas close to drainage (valleys, floodplains)</li>
  <li><strong>Higher values</strong> represent elevated terrain (ridges, uplands)</li>
  <li>This is a <strong>relative terrain measure</strong>, not absolute elevation</li>
  <li>Focus on <strong>low-value zones</strong> where water is more likely to accumulate</li>
</ul>

<p><strong>Key Insight:</strong> Lower positions relative to drainage are more likely to retain water and increase exposure.</p>
<h4>Units of Measure</h4>
<p>Meters (m)</p>

<h4>Technical Specification</h4>
<p>
This dataset represents Height Above Nearest Drainage (HAND), a hydrologically meaningful terrain metric used to identify low-lying drainage-connected environments, floodplain position, and areas with elevated potential for water accumulation.
</p>

<p>
Unlike absolute elevation, HAND measures vertical position relative to the local drainage network. Lower HAND values indicate terrain closer in elevation to nearby drainage channels, while higher values indicate elevated or better-drained terrain.
</p>

<h4>Key Characteristics</h4>

<ul>
  <li>Represents vertical distance above nearest drainage</li>
  <li>Low values indicate floodplain or valley-bottom terrain</li>
  <li>High values indicate elevated or well-drained terrain</li>
  <li>Supports hydrologic exposure, saturation, and drainage-position modeling</li>
  <li>Primary physical driver in the Pipeline Hydrologic Exposure model</li>
</ul>

<h4>Spatial Characteristics</h4>

<ul>
  <li><strong>Coordinate System:</strong> GCS_WGS_1984</li>
  <li><strong>Spatial Resolution:</strong> ~1 km</li>
  <li><strong>Coverage:</strong> Global</li>
  <li><strong>Format:</strong> GeoTIFF / web raster</li>
</ul>

<h4>Processing</h4>

<p>
The HAND raster was derived using terrain elevation, drainage network structure, and flow-routing relationships. Processing included:
</p>

<ul>
  <li>DEM conditioning and sink filling</li>
  <li>Flow direction modeling</li>
  <li>Drainage channel identification using upstream contributing area</li>
  <li>Vertical flow-distance calculation to nearest drainage</li>
  <li>Export to global raster format for hydrologic exposure modeling</li>
</ul>

<h4>Interpretation</h4>

<table border="1" cellpadding="6" cellspacing="0">
  <tr>
    <th>HAND Value</th>
    <th>General Interpretation</th>
  </tr>
  <tr>
    <td>Low</td>
    <td>Near drainage elevation; likely floodplain, valley-bottom, or saturation-prone terrain</td>
  </tr>
  <tr>
    <td>Moderate</td>
    <td>Intermediate terrain position with partial drainage influence</td>
  </tr>
  <tr>
    <td>High</td>
    <td>Elevated terrain with reduced hydrologic exposure potential</td>
  </tr>
</table>

<h4>Role in Pipeline Hydrologic Exposure Model</h4>

<p>
HAND is one of the primary inputs used to identify terrain where buried pipelines may experience elevated hydrologic exposure. Low HAND values are associated with conditions more favorable to prolonged soil moisture, reduced aeration, and potential saturation-related corrosion mechanisms.
</p>

<p>
This raster directly supports the derivation of:
</p>

<ul>
  <li>HAND Low-Lying Index</li>
  <li>Saturation Potential Index</li>
  <li>Drainage Position Index</li>
  <li>Pipeline Hydrologic Exposure Score (1–100)</li>
  <li>Pipeline Hydrologic Exposure Index (1–7)</li>
</ul>

<h4>Scope and Intended Use</h4>

<ul>
  <li>Floodplain and valley-bottom screening</li>
  <li>Pipeline hydrologic exposure assessment</li>
  <li>Terrain-driven saturation analysis</li>
  <li>Drainage-connected landscape interpretation</li>
  <li>Supporting input for pipeline corrosion screening models</li>
</ul>

<p>
This dataset is a terrain-derived hydrologic indicator and is not a regulatory floodplain map or flood-depth model.
</p>

<h4>Related Hydrologic Exposure Datasets</h4>

<h5>Primary Hydrologic Exposure Indices</h5>

<ul>
<li><a href="https://secure.engineeringdirector.com/public/map/Pipeline_Hydrologic_Exposure_Score_1_100_v14_final">Pipeline Hydrologic Exposure Score (1–100)</a></li>
<li><a href="https://secure.engineeringdirector.com/public/map/Pipeline_Hydrologic_Exposure_Index_1_7_v14_INT_websafe">Pipeline Hydrologic Exposure Index (1–7)</a></li>
</ul>

<h5>Supporting Hydrologic Input Layers</h5>

<ul>
  <li><a href="https://secure.engineeringdirector.com/public/map/HAND_Height_Above_Nearest_Drainage_m">HAND – Height Above Nearest Drainage</a></li>
  <li><a href="https://secure.engineeringdirector.com/public/map/HAND_Low_Lying_Index_0_1">HAND Low-Lying Index</a></li>
  <li><a href="https://secure.engineeringdirector.com/public/map/Saturation_Potential_Index_0_1">Saturation Potential Index</a></li>
  <li><a href="https://secure.engineeringdirector.com/public/map/Drainage_Position_Index_0_1">Drainage Position Index</a></li>
  <li><a href="https://secure.engineeringdirector.com/public/map/River_Influence_20km">River Influence</a></li>
  <li><a href="https://secure.engineeringdirector.com/public/map/Distance_To_River_20km_Geodesic">Distance to River</a></li>
  <li><a href="https://secure.engineeringdirector.com/public/map/Drainage_Index_Normalized_0_1">Drainage Intensity Index</a></li>
</ul>

<h4>Limitations</h4>

<ul>
  <li>HAND represents relative terrain position, not flood depth.</li>
  <li>It does not predict flood frequency or storm-event inundation.</li>
  <li>It does not account for engineered drainage, levees, or local flood-control infrastructure.</li>
  <li>It should be interpreted as a terrain-based hydrologic screening layer.</li>
</ul>

<h4>Legal & Licensing</h4>

<p>
© 2026 AtmosphericIQ LLC and Engineering Director, Inc. All rights reserved.
</p>

<p>
This dataset and associated models are proprietary to AtmosphericIQ LLC and distributed by Engineering Director, Inc.
</p>

<h4>Dataset Citation</h4>

<p>
Mazzella, J. (2026).<br>
<strong>HAND – Height Above Nearest Drainage, Global Raster.</strong><br>
AtmosphericIQ LLC / Engineering Director, Inc.
</p>

<p>
Derived using terrain-based hydrologic analysis, drainage network extraction, flow direction modeling, and global DEM processing.
</p>

---

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