Seep City details

Seep City Map of Water Explorations and the Seep City Water Log book are print publications of San Francisco water historian and explorer Joel Pomerantz, founder of Thinkwalks.  415-505-8255

Here are some ways to participate in citizen science about SF water:
⌑ Contact Joel with observations of San Francisco springs, seeps, etc.
⌑ Have Joel present to your group or lead an exploration for your group.
⌑ Introduce your community to the Seep City map via a post, link, review or email.
⌑ Make a donation to support water research.
⌑ Ask your bookstore to carry the Seep City Water Log book when it comes out.

About the project

This map was produced as a companion to the forthcoming book, Seep City Water Log.

The project incorporates these root concepts:
⌑ Art can engage the explorer's mind.
⌑ Direct contact with the landscape is deeply healthy.
⌑ Society is richer and more resilient when citizens participate in science and history.
⌑ The ideals of civic journalism compel a careful evaluation of evidence.
⌑ History, rife with mistakes and biases, presents opportunities for rethinking conventional assumptions.
⌑ Discovery is empowering.

During Joel's decades of exploration and data collecting, he always sought to make his findings available to other curious San Franciscans. He leads Thinkwalks and shares in community knowledge base projects, debunks myths and spreads rumors (always doing his best to clarify the evidence, or lack thereof). This is all part of the process of introducing the convolutions of natural history to a data-driven, frenetic community.

With the Seep City project, Joel's collected knowledge has finally taken a tangible form. Huge thanks go out to many volunteers, supporters, friends and colleagues for your encouragement and participation!

How the map was made

Joel hand-traced the water and shores from old maps and surveys (1852, 1859 and 1869) using Photoshop. The land is a detailed contour map adapted by graphic designer Abe Bingham from 2002 data provided by the city. The legend design is by Abe. The Bay water lines and other map features are Joel's.

This map is based on research that includes stomping in mud through brambles, excavating archival material and tracking oral and written anecdotes. Metadata for this map is not in the usual form that cartographers use for digital map-making. The map shows color differences based on whether the waterway was sourced from US Coastal Surveys or from other materials. Sources include photos, commercial maps, landform and vegetation clues, oral histories and newspaper columns.

All waterways are shown under wet year conditions.

Technical specifics

Contour lines are shown at intervals representing a separation of five feet apart in elevation. Contours date to December 2001 measurements. A parallax-based 3D surface model was created in January 2002 at the SF Department of Public Works from aerial photos by Hammon, Jensen, Wallen & Assoc., a.k.a. Pacific Aerial. Abe Bingham has rectified the contours to match a few of the landscape changes made since.

Historic shores are based on US Coastal Survey Maps, as follows.

⇢ From 1869 survey: west of Pierce Street, south of Islais Creek.
⇢ From 1859 survey: Pierce Street to Leavenworth Street, Harrison Street to Islais Creek.
⇢ From 1852 survey: Leavenworth Street to Harrison Street.
⇢ Today’s shores, piers and bridges are based on Google maps February 2015.

Tidal marshes

⇢ From 1869 survey: northern marshes, Yosemite Creek Marsh.
⇢ From combined 1852 and 1859 surveys: Mission Creek.
⇢ From combined 1859 and 1869 surveys: Islais Creek Marsh.
⇢ From 1852 survey: marsh emptying into north edge of Mission Bay.

Some marsh infill certainly occurred from 1776 to 1852, but reliable records are unavailable. West of Harrison Street at Mission Creek, it was necessary for Joel to make some informed guesses in depicting original marshlands. The term “original” is a moving target in any case.

Content license

Map created by Joel Pomerantz in San Francisco, California, 2015.

You hereby have permission to use small clip images from the map, but only for the following purposes:
⌑ You may present and describe the map in media, if it's kept available free without subscription.
⌑ Any use of the map that follows the licensing rules below.

All other uses must receive permission from Joel Pomerantz. Currently a full digital copy of the map is available only by arrangement.

Seep City Water Exploration Map is licensed under a Creative Commons license:

Creative Commons

Attribution-Noncommercial-shareAlike 4.0 International

This means you may reproduce this work or portions of it, or make derivatives of it, with these conditions:
⌑ You agree to use the material only for nonprofit uses.
⌑ You agree to attribute the material to Seep City Water Exploration Map by Joel Pomerantz.
⌑ If your attribution or use is online or in email, you include a link to
⌑ If changes were made, you must indicate that.
⌑ If you remix, transform, or build upon the material, you must distribute your result under the equivalent license to the original Creative Commons Attribution-Noncommercial-shareAlike 4.0 International.